Hub, it sounds like this is a tough time for both of you.
I really wish I knew how to advise on finding a hobby, but there's a lot of complexity in your lives right now...magnified by an uncertain prognosis. I do think that some level of light physical exertion would help his depression...
As a man, I want to say "Is it possible that he's lonely and scared...and using the idea of a hobby as a 'red herring' for more companionship." BUT, your "bossing around" comment really bugs me about whether he's being sincere or not...and that's why I don't know what to say...
If you don't grow where you're planted, you'll never BLOOM - Will Rogers