Solid work Mike. I'll second Mike's suggestion of taping up those thumbs. Never felt as though my thumb rolled, but the tape makes the hook grip a lot more comfortable and also gives your index and middle finger some traction. As for tape, athletic tape with some stretch is usually best but also harder to come by. Past that regular 'ol athletic tape will work well enough, you'll just have to force your thumbs into that bent position to loosen up the tape after applied.
For the snatch grip. It'll be tough especially if you have small hands. Grip should open up over time as flexibility with the hook increases. Bar position with it just hanging should be at the waist line. I'd go with straps if its holding you back.