There is probably something that he feels is a reason for ending the friendship. You may never know and can't make him tell you. Maybe he isolates and wants to be alone. You've already reached out, but been asked to stay away, so should respect that. Maybe you could send a final note that the door is open if he changes his mind, but no pressure.

Living with bp and having children with bp, I wouldn't call it an oddity. Maybe living with it makes it not seem odd to me. But what I know about it, yes it shows up in childhood. Bp people also can go along lengths of time without any symptoms, then usually something sets it off because of our deep sensitivity in my opinion.