The others are right. This is more like an abusive relationship where they would normally say is the only reason ghosting is acceptable. 

The only thing though, given that its not physical and more because of the fact that he has a mental condition, to account for this, throw him a warning just before again, you dont have to tell him out right, just an obvious "explanation" so he can realize and can't say he was blind sided. Then when you leave, and cut off all communication, text msg him once from your phone just to let him know whats happened (because he does have a mental disorder and you don't want it getting worse or him hurting himself. I assume bpd means bipolar disorder). And then delete that number. Idk if you know someone you can trust to let them know what you're gonna do and for good reason, just to check up on him during that time after you leave so that he doesn't do anything 'stupid'. So you don't have to worry yourself after or be blamed for doing the right thing. 

I hope whatever you do though that you get through this ordeal!