If AC is a concern, I'd switch the 15 and +1 to Dex instead of Con. This character is going to have more than enough HP, the AC, Reflex saves, and initiative from Dex will help more, especially with the AC bonus from whirling frenzy. Taking four more levels of fighter for dungeoncrasher is definitely not worth it. Swapping Power Attack for Stone Power is very anti-synergistic with Knockback and Shock Trooper, I don't recommend it, either. There are some other feats that are useful in general for throwers, but this build is already feat-constrained.