This individual is emotionally abusing you. And you are letting him do this to you when you interact with him.

It's concerning to me why you continue to engage at all. You need to cut him off completely and that's it, there is no relationship at all with this individual that you can possibly have. How much proof do you need to understand that? Let him blow himself up or whatever. Your are pushing a mountain that simply cannot be moved.

The other thing is that you really do not know if this is borderline, it could be a few things, even something that is mixed in with OCD because he is compulsive. He may also have something that is accompanied with psychotic features or episodes. His mental state is simply beyond you and it's safest for you to stop interacting with him completely.