I Catlover

I didn't have an experience like that but I am myself BPD and very conscious about it. About the girl, it is clearly made up. When you "let him down" about going to see him, it would normally cause anyone to feel disappointed, which is a nornal thing to feel when you want something to happen and it ends up not happening. But his ability to deal with that emotion might not be that good and probably interpreted it has "you not wanting to see him" or anything that has to do with the fact that he's not that interesting to you. We have to face the facts, his expectations are a bit unrealistic, first of all, he should clear things up in his life and then consider having a relationship. The way he told you about that other girl sounds like a fantasy.. Perhaps a version of you being available for him to be with, exposing it to you to make you feel bad about not going to see him even tho you didn't have much control over it.
Now this is not entirely intentional, tho.
I would suggest to think about what YOU want, regardless of his thoughts or reactions. Just, ideally, what would you like, you know?
And if you feel like you want to keep doing this, it'd be important to have a serious talk with him, and if he doesn't respond well, like being avoidant or defensive, then he might not be ready to have you around even tho he's been seeking your presence.