Sounds exactly like me sometimes. When I'm manic I love to pick fights with the gf about anything. One day we had a huge heated argument about socks. Yes socks! Something so trivial turned into a huge argument and i did pull the "you don't love me..." act too. I tend to pull it out in fights like these. I do feel bad because the gf is in your exact shoes; logic doesn't work or help, arguing only makes it worse, and ignoring me just pisses me off.

What has helped me a lot is seeing a therapist once a week. It originally started as therapy for my bipolar but it has moved into a hybrid couples counseling and that's actually made our relationship better. It helps her deal with me when my mood is all over the place and it helps me control my anger and my behavior, while seeing things from her point of view.

Maybe therapy is something you two (or at least he) could try.