Couple of mistakes in the pattern:
Part 1 Round 5 should start in the third stitch of the petal - I also changed the Tr-cluster to 2tr
Part 2 Round 1 should be work 13dc along the side between corners if working the clusters on the previous round - because I did 2tr instead, each side had 15dc

For the brim, work dc around then change to smaller hook for ribbing