IHW is one of those effects where the implication is that you can't wriggle out of taking the damage, although presumably appropriate DR or energy resistance/immunity would see you through. Also I second the motion a few people have made above that with IHW you are taking the bullet, not just defending someone more effectively.
Crucially, though, you just can't use both feats at once as they require different and discrete standard actions. Aid Another is a standard action and Fighting Defensively/Total Defense is at least a standard action and therefore never the twain shall meet.