What happened to him is none of your fault. Never blame one side, blame both.
If he has a personality disorder, it has a possibility of worsening if not treated, and if it's that bad to affect his relationships, he should get help, instead of suffering himself, and making others suffer around him.

The best thing to do is go separate ways. You are not the problem, the both of you are. It is just not meant to be, you both are making each other miserable.
A man shouldn't make his woman feel worthless, sad, or anything negative at all.
Leaving would be the best option, it's going to be the better choice long term.
Take care.