I was once 'seeing' someone who I didn't like very much. I had a lot of difficulty letting him go though. In fact I spent about 3 years obsessing about him, and yet I didn't even really want him

In my case, I think it was because I didn't have much else going on in my life. His attention (what little there was of it) was exciting.
Also, I think I was just obsessed with getting him to like me (even though I didn't really like him

It sounds like in your case there might also be a little bit of wanting to "save him" from his inner demons. But by the sounds of it he really doesn't want you to!.
I eventually had to go 'no contact'. I did this for an initial period of 3 months, most of which time I spent crying

However I did have enough sense to also take that time to get myself more of a life. The more time I spent with other people, the more I got over him.
So, to answer your question, no, I don't think this 'friendship' can be salvaged, since really (unless there is more to the story than you've told) he's not really much of a 'friend' to begin with.