A lovely design.
Superbly written.
Makes up quickly.

Note:
An in-the-round swatch, washed / dried as the garment is imperative.

This yarn: machine wash / tumble dry:
I had two different lots. One shrank and felted profoundly. The other shrank some, but retained shaping.

This sweater was made from the non-felting lot. Allowed for shrinking.

Added four stitches to main section and two to each sleeve in order for 6 stitches at underarm vs 4.
Worked sleeves flat and seamed with sl st crochet.

For me, the neckline stitches looked better when on the purl row, p2tog tbl at the end of the row.
I had an odd # stitches at start of neckline shaping, where the pattern calls to cast off 3 at the center divide. I wish I had cast off just one, because the neckline is somewhat squared off at the bottom and then a V going up. Worked one row sc and one row sl st crochet around neckline in order to round out the front neckline.