Having a close person with anger problems can be awfull, i suffer from that too, suffered it all my life, a shame, you are very lucky that he is trying to do something about it, i didnt have that luck...
Try EFT, it can be done by himself, its fast, powerfull, almost miraclous, read this
Using EFT for Rage & Anger Management, despite the werid aspect of it and its incredible promises, it really works.
Good luck.