The best advise I can offer is to work on you. BPD is such a draining, sad and distressing mental illness and there's no way to make someone go to therapy and actually gain something from it unless they are really wanting it.
I know my situation is mild comparatively (some stories I've heard here make me want to jump through the computer and save people... .maybe it's good that I can't!

The only thing I've been able to do is change the way I react to his rantings. I'm me and he either accepts it or he can kiss my butt. I've no reason to think he will change. I don't care if he does. I stay because the good times far outweigh the bad. I hope you have enough "self" to go to therapy on your own and see where that takes you. Wishing you happy days ahead!