REALLY Really challenging for me, and I know all the stitches. I think part of the problem (MY problem) was that the language used was not standard American crochet. I dunno- could be all wet on that.
Did a lot of tear out, most of it my fault, some of it just not quite understanding what I was being told. Lots of mistakes here as one can see. Would like to make another correctly, now that I “get it.” (Kinda like golf, ya know?)
Rewrote the problem areas for myself, and including my rewrite such that it may help others. KNOW this includes notes intended for myself. If others find some helpful notes here, that’s awesome.I recommend one starts with the original pattern and use my notes for clarification.
Here it is in its entirety:
(The comments from others who tackled this project were really helpful; thank you all!!)

Approximately 6.5”at widest point across bottom of bib and 10” long from top of shoulder to bottom peak of V measuring straight up the centre, not including ties. Neck circumference approximately 9.5”, not including ties. To make it bigger I suggest using a thicker yarn and larger hook.
Gauge
Approximately 21 st and 13 ridges to 2” when worked in ridged dc.
Materials
50g ball of Size 3 Thread. I used Aunt Lydia’s Crochet Thread Fashion 3
20g ball of mercer crochet size 40 for the edging
(Size 10 in USA)
1.5 mm crochet hook
0.9 mm crochet hook for the edging
Needle to tidy away ends

Abbreviations
ss slip stitch (US slip stitch)
ch chain (US chain)
dc double crochet (US single crochet)
tr treble (US double crochet)
yoh yarn over hook
Dec Decrease – in first st work 1 dc but do not finish off last 2 loops, work 1 dc in next st, finishing off both dcs together. (2 dcs reduced to 1)

Special Stitch
p picot – 4 ch, 1 dc into top left-hand side of the st where the first ch came from. Begin the dc by inserting the hook behind the front loop of the top of the st and then behind the top-left thread of the post of that st, continue with dc as usual.
sm sh small shell – (1 tr, p, 1 tr, p, 1 tr, p, 1 tr) all in the same space.
sh shell – (1 tr, p, 1 tr, p, 1 tr, p, 1 tr, p, 1 tr) all in same space.

Notes: The turning chains are not counted as stitches unless noted otherwise.
Always work in the back loop unless told otherwise.
When working the 31 dc down each side of the Central Panel you will get the tidiest, most evenly-spaced effect if you insert your needle to catch the free loop of the first st of the ridge on the front side for every other st and then for the in-between stitches insert your hook so that it also catches the free loop of the first st of the ridge on the other side. You might have to experiment a couple of times to get the placement just right. If you get a tidy effect but are one stitch over or under then increase or decrease a stitch in the middle of that section when you do the next row. HUNH?

Central Panel
Row 1: ch 34, working under both top loops of the ch (working in “back loop” for me); 1 dc into 2nd ch from the hook, 15 dc, 3 dc in centre st, 16 dc, ch 1, turn. (35 sts plus 1 turning ch)
Row 2: Remembering to crochet in back loops:
35 dc, 1 ch, turn. (35 sts plus 1 turning ch)
Row 3: Dec, 15 dc, 3 dc in centre st, 15 dc, dec, 1 ch, turn. (35 sts plus 1 turning ch)
Row 4: 35 dc, 1 ch, turn. (35 sts plus 1 turning ch)
Row 5: Dec, 15 dc, 3 dc in centre st, 15 dc, dec, 1 ch, turn. (35 st plus 1 turning ch)
Row 6: 35 dc, 1 ch, turn. (35 sts plus 1 turning ch)
Row 7: Dec, 15 dc, 3 dc in centre st, 15 dc, dec, 1 ch, turn. (35 sts plus 1 turning ch)
Row 8: 35 dc, 1 ch, turn. (35 sts plus 1 turning ch)
Row 9: 17 dc, 3 dc in centre st, 17 dc, 1 ch, turn. (37 sts plus 1 turning ch)
Row 10: 37 dc, 1 ch, turn. (37 sts plus 1 turning ch)
Row 11: Dec, 16 dc, 3 dc in the centre st, 16 dc, dec, 1 ch, turn. (37 sts plus 1 turning ch)
Row 12: 37 dc, 1 ch, turn. (37 sts plus 1 turning ch)
Row 13: Dec, 16 dc, 3 dc in the centre st, 16 dc, dec, 1 ch, turn. (37 sts plus 1 turning ch)
Row 14: 37 dc, 1 ch, turn. (37 sts plus 1 turning ch)
Row 15: Dec, 16 dc, 3 dc in the centre st, 16 dc, dec, 1 ch, turn. (37 sts plus 1 turning ch)
Row 16: 37 dc, 1 ch, turn. (37 sts plus 1 turning ch)
Row 17: 18 dc, 3 dc in centre st, 18 dc, 1 ch , turn. (39 sts plus 1 turning ch)
Row 18: 39 dc, 1 ch, turn. (39 sts plus 1 turning ch)
Row 19: Dec, 17 dc, 3 dc in centre st, 17 dc, dec, 1 ch, turn. (39 sts plus 1 turning ch)
Row 20: 39 dc, 1 ch, turn. (39 sts plus 1 turning ch)
Row 21: Dec, 17 dc, 3 dc in centre st, 17 dc, dec, 1 ch, turn. (39 sts plus 1 turning ch)
Row 22: 39 dc, 1 ch, turn. (39 sts plus 1 turning ch)
Row 23: Dec, 17 dc, 3 dc in centre st, 17 dc, dec, 1 ch, turn. (39 sts plus 1 turning ch)
Row 24: 39 dc, 1 ch, turn. (39 sts plus 1 turning ch)
Row 25: 19 dc, 3 dc in centre st, 19 dc, 1 ch, turn. (41 sts plus 1 turning ch)
Row 26: 41 dc, 1 ch, turn. (41 sts plus 1 turning ch)
Row 27: Dec, 18 dc, 3 dc in centre st, 18 dc, dec, 1 ch, turn. (41 sts plus 1 turning ch)
Row 28: 41 dc, 1 ch, turn. (41 sts plus 1 turning ch)
Row 29: Dec, 18 dc, 3 dc in centre st, 18 dc, dec, 1 ch, turn. (41 sts plus 1 turning ch)
Row 30: 41 dc, 1 ch, turn. (41 sts plus 1 turning ch)
Row 31: Dec, 18 dc, 3 dc in centre st, 18 dc, dec, 1 ch, turn. (41 sts plus 1 turning ch)
Fasten off work leaving a 15 cm tail and turn it over so the Wrong Side will be facing when you join the Border to it.

Border

Row 1: Ch 36, joining at narrow end (this is on the future “top” of the bib in my world) of central panel on the Wrong Side and working over the starting tail of that panel do 31 dc along the side, 3 dc into first st on top (my bottom) edge, 39 dc, 3 dc into last st of top (my bottom) edge, do 31 dc down other side of central panel, 37 ch, turn. (179 sts plus 1 turning ch)

(Here, original pattern explains how to work over long tail to gather and straighten the work. I did this the first time but didn’t find it necessary. Blocking the final piece worked for me.)

Row 2: Working under both top loops of the ch; 1 dc into 2nd ch from hook, 16 dc, 3 dc in next ch, 18 dc, working into back loops again now, 32 dc, 3 dc into centre st of group of 3 dc, 20 dc, 3 dc into next st, 20 dc, 3 dc into centre st of group of 3 dc, 32 dc, working under both top loops of ch, 18 dc, 3 dc in next ch, 17 dc, ch 1 turn. (189 sts plus 1 turning ch)
Row 3: 1 dc into each st to the end, ch 1, turn. (189 sts plus 1 turning ch)
Row 4: 18 dc, 3 dc in next st, 52 dc, 3 dc in next st, 22 dc, 3 dc in next st, 22 dc, 3 dc in next st, 52 dc, 3 dc in next st, 18 dc, ch 1, turn. (199 sts plus 1 turning ch)
Row 5: 1 dc into each st to the end, ch 1, turn. (199 sts plus 1 turning ch)
Row 6: 19 dc, 3 dc in next st, 54 dc, 3 dc in next st, 24 dc, 3 dc in next st, 24 dc, 3 dc in next st, 54 dc, 3 dc in next st, 19 dc, do not turn. (209 sts)
Row 7: Do an American Double Crochet instead of all this: (Insert hook from far side to near side into front loop of st just worked, yoh, pull through a loop, turn, yoh, draw through both loops on hook, (1 dc into left-hand side of st just made) twice, (all for 1st tr), 2 ch, skip 1 st, dc in next st, 2 ch, skip 1 st, 3 tr. Repeat from ending row with 2 ch, skip 1 st, dc in next st, 2 ch, 1 tr last st, 1ch turn. (34 complete sets of 3 tr plus end stitches)
Row 8: 1dc in first st, 3 ch, 1 dc in each of next 3 tr. Repeat from ending with 3 ch, 1 dc in top of special st made to stand in as 1st tr at the start of the previous row, 1 ch, turn. (209 sts plus 1 turning ch)
Row 9: Working into back loops of dcs and top two loops of chs; 20 dc, 3 dc in next st, 56 dc, 3 dc in next st, 26 dc, 3 dc in next st, 26 dc, 3 dc in next st, 56 dc, 3 dc in next st, 20 dc, 1 ch, turn. (219 sts plus 1 turning ch)
Row 10: 1 dc into every st, 1 ch, turn. (219 sts plus 1 turning ch)
Row 11: 21 dc, 3 dc in next st, 58 dc, 3 dc in next st, 28 dc, 3 dc in next st, 28 dc, 3 dc in next st, 58 dc, 3 dc in next st, 21 dc, 1 ch, turn. (229 sts plus 1 turning ch)
Row 12: 1 dc into every st, 1 ch, turn. (229 sts plus 1 turning ch)
Row 13: 1 dc in 1st st, 2 ch, skip 1 st, 3 tr, 2 ch, skip 1 st, 1 dc, 2 ch, skip 1 st. Repeat from ending with 3 tr 2 ch, skip 1 st, 1 dc, 1 ch, turn. (38 complete sets of 3 tr plus end stitches)
Row 14: 1dc in first st, 1 ch, 1 dc in each of next 3 tr, 3 ch, 1 dc in each of next 3 tr. Repeat from ending with 3 ch, 1 dc in each of next 3 tr, 1 ch, 1 dc in last st of previous row, 1 ch, turn. (229 sts plus 1 turning ch)
Row 15: Working into back loops of dcs and top two loops of chs; 22 dc, 3 dc in next st, 60 dc, 3 dc in next st, 30 dc, 3 dc in next st, 30 dc, 3 dc in next st, 60 dc, 3 dc in next st, 22 dc, 1 ch, turn. (239 sts plus 1 turning ch)
Row 16: 1 dc into every st, 1 ch, turn. (239 sts plus 1 turning ch)
Row 17: 23 dc, 3 dc in next st, 62 dc, 3 dc in next st, 32 dc, 3 dc in next st, 32 dc, 3 dc in next st, 62 dc, 3 dc in next st, 23 dc. (249 sts)
Fasten off, leaving a 6” tail.

Neckline AND Ties:
Start with Right Side facing, do NOT work through the back loop.
Row 1: 60 ch, working over the beginning tail of the Border; 1 dc in the base of every stitch on the inside neck edge skipping the stitches that had 3 dc worked into them originally, drop tail, 61 ch, turn.
Row 2: Working into the back ridge of the chs (working in “back loops” worked fine here also) ; 1 dc into the 2nd ch from the hook, 1 dc into every stitch to the end.
Fasten off, leaving a 6” tail.

Edging
Using size 10 thread in USA
Start with Right Side facing, leaving a 6” tail.
Row 1: 1 ss at corner where the short end of the Border and Tie meet, 10 ch, catching just one thread on the edge 1 ss (the same size as the ch) into the middle of the end of the Border, 10 ch, 1 ss at corner and outer edge of the Border, 1 ch, turn.
Hold the work now so that the ch can act as a guide to evenly space the following stitches along the short edge of the Border: Working under both top loops of each ch and catching just one thread of the Border edge do 10 dc,* 1 dc in same place as ss. Repeat from * to ****, 1 ss in corner where the Border and Tie meet. You have 21 evenly spaced and very tidy dc on the end of the Border, 1 ch, turn.
Working in back loops now: 1 dc in first st, 2 ch, skip 2 sts, 1 dc. Repeat from6 more times, 1 dc in first st of outer edge of border. Do not turn.
Working along outer edge of border, and still in the back loops: 2 ch, skip 1 st, 1 dc. Repeat from to last st of outer edge of border, 1 ss at the corner of the short end and outer edge of the Border.
10 ch, catching just one thread on the edge 1 ss (the same size as the ch) into the middle of the end of the Border, 10 ch, 1 ss at corner of the end of the Border and tie, 1 ch, turn.
Hold the work now so that the ch can act as a guide to evenly space the following stitches along the short edge of the Border: Working under both top loops of each ch and catching just one thread of the Border edge do 10 dc,* 1 dc in same place as ss. Repeat from * to , 1 ss in corner where the short end and outer edge of the Border meet. You have 21 evenly spaced and very tidy dc on the end of the Border, 1 ch, turn.
Working in back loops now: 1 dc in first dc, 2 ch, skip 2 sts, 1 dc. Repeat from6 more times, 1 ch, turn. (138 2-ch loops)

Row 2: Do not work in back loops.
1 dc in first 2-ch loop, 1 ch, 1 sm sh in next 2-ch loop, 1 ch, 1 dc in next 2-ch loop. Repeat from twice, 1 dc at corner, p, 1 dc in next 2-ch loop, 2 ch, 1 sh in next 2-ch loop, 2 ch, 1 dc in next 2-ch loop, p, 1 dc in next 2-ch loop.
Repeat from twice, 2 ch, 1 sh in next 2-ch loop, 1 ch, skip next 2-ch loop, (1 tr, p, 1 tr, 1 ch), in next dc (between 2-ch loops at the next corner), 2 ch, skip next 2-ch loop, †1 sh in next 2-ch loop, 2 ch, 1 dc in next 2-ch loop, p, 1 dc in next 2-ch loop, 2 ch.
Repeat from † 9 more times, 1 sh in next 2-ch loop, 2 ch, 1 dc in next 2-ch loop, 2 ch, ††1 sh in next 2-ch loop, 2 ch, in next 2-ch loop work 1 dc, p, 1 dc in next 2-ch loop, 2 ch.
Repeat from †† 4 more times, 1 sh in next 2-ch loop, 1 ch, skip next 2-ch loop, (1 tr, p, 1 tr, 1 ch), in next dc (between the 2-ch loops at the next corner). Complete second half of Row 2 to mirror image the first half. (6 sm shs, 34 shs)

Edging Variations You can make the shells taller by using double trebles (US trebles) and fuller by using more stitches in each shell. If the small shells on the short ends of the Border seem too skimpy substitute them with full-size shells. At my tension with my thread full-size shells were just a little bit too crowded.

Finishing
Weave in all tails for a few cms using a needle on the wrong side, running them through the dcs and changing direction at least once. Do not cut off the excess until the bib has been washed and blocked. When blocking encourage the bib to lie flat but do not stretch the ribs out too much. Allow them to remain distinctly ridged.
If you press do so from the wrong side on a well-padded surface so that the stitches are not flattened.