You've got a heart of gold
ivinsfan - IMO you've gone way above and beyond.
I read most of the posts and see that you do care about friend, but I have to truly wonder how much friend cares about you.
Like you, I have the oldest female child problem of wanting to rescue everyone. And I've had "friends" like this too; call me up and "boo hoo - I've got a problem, I don't know what to do, I need help" but when help is suggested, solutions are offered, all is ignored and excuses are made.
When it begins to feel like I'm beating my head on a brick wall I'm done.
Looks to me like you're beginning to feel like that as well. I know this is easier said than done, but at some point you really just have to walk away in order to preserve your own mental health.
Three years of trying to help met by three years of excuses is, for me about 35 months too long.
If I were in your place I would tell friend I'm at the end of what I can do, he's not willing to work toward the solutions I, DH and whomever else have tried to come up with, so I'm sorry but I'm finished and at that point I would just stop answering the phone or the door if he calls or comes around.