So... I emailed the other girl - she had NO idea of my existence, and we just spoke on the phone.
When she got my email, she was at his place, and was understandably freaking out - but he wasn't home. She wound up confronting him, and he said I was a "crazy bitch". Funny thing is, neither she nor I are crazy. He is. And refuses to address his issues.
Good riddance to bad rubbish.