Aim offset makes mesh go haywire

Hello,
Let me start by saying i have not seen much help for this kind of thing, so I figured id post.

Thats my guy, after putting him in an aim offset. He looks fine, doing his t-pose. I thought it was weird though since I set the default pose to holding his gun at the hip, and he continued to t-pose. Then i added a pose to the grid:

He goes crazy, and it only gets worse as I fill out the grid. Even with the hip pose in each part. Any help? I would like to fix this!