1. I think ninja could be a good sub(but you can only get it at lvl 30) if not you can take warrior(should adds you some vit,str,dex)

2. Mithra are definetly the best followed by humes, but remember to play a race that you feel good with not only for its stats.

3. I saw on other forums that the drop rate was 10% higher with a thief in the 20s.