Wow Jen that is quite over the fence. From the patients view I can kinda relate to what your husband is feeling. First of all I need to say I am very grateful for my life. I am not a phsyciatrist nor and am not male but am finding being "limited" is extremely frustrating.
I have experience with my son who has anger issues and the more dangerous the activity the better he feels. It has been scary to watch these extreme sports. I opted for putting him in group sports helped . I know I will be able to get back to "normal" life soon but it doesn't seem soon enough. I also understand the need to get out aggression. I too am not nor have ever been an aggressive person but it does build up. Hopefully you can talk to him about maybe something not quite as drastic but will allow him to regain some of what he considers manhood...Does he have a male friend that he could maybe just spar with or another activity that seems to get rid of agression is believe it or not go carting...sounds simple but for some reason it worked for my husband and son. There are a lot of things that would have the same effect but less brutal...
Maybe a male friend to help do a high energy activity with him
and he might open up to his friend guys do that hopefully he has a close male bonding type friend maybe this might help.