Well, my Df is on meds and going to T. But in some ways, I feel like he is staying sick, partially because he really feels like he can't get better (he has told me this), and partially because remaining sick means he does not have to deal with anything else in his life. Does that make sense?

Yes, that makes total sense. Mine has been "trying" with meds and therapy, but it is like it is something being done to him-not something he is taking ownership of. We once had a "discussion" about denial. He said he has never denied his depression or anxiety. Yes, he has not denied the symptoms, but he has not fully accepted responsibility for it either. If he isn't responsible for its orgins or its continuation, he doesn't have to do anything about it-really.