I'm A Fraud.....

[Sperwer]

I think you are all on a wrong track- his problems most likely comes from "mental side" and that is where he needs to concetrate most, solving underlying issues and root of the problem, ignoring problem and concentrating on gym will make it easier but eventually he'll be in same situation again.
Plus, his CNS is taking battering right now, heavy exercise will tax it even more and deplete his body of much needed chemicals (hormones etc...)
He need to start slowly and make 5 year plan, "progressive loading" is the word.

Agreed that the actions we've recommended don't go to the root of the problem, and all DELIBERATE speed is the watchword; but done mindfully they are palliatives that will relieve the symptoms and their consequences and open up a space for the other work