I don't see that behavior as a bipolar issue, IMO. Never have come across it.

I think the fact that the two of you broke up 9 months ago but remain in contact may be the problem. On a certain level, the two of you are still enmeshed and it triggers negativity for him, it appears. And he's projecting that negative behavior on you. No win situation.

A final, clean break may be best. I'm not friends with my ex's....no ill will. Just when it's over, it's over.

Hope that helps. Just my perspective.