I like your hat and think the rib looks better and will give you the fit you want better than garter stitch, good call on a modify! Sorry 'bout the yarn weight mix up but the hat is gorgeous! So what about the sweater?
Cheating is an option. . . . Cheaters never win and winners never cheat, but smart knitters who want to retain an iota of sanity do, cheerfully. ~~Kory Stamper