Thanks for the advice.
I agree with you about trusting instincts, but on the other hand it was a long time ago when he was only 20, and I don't know both sides of the story (the girl has since proved a little weird herself). I did some pretty rash things when I was younger that I would never repeat. Hard to judge. Don't want to be the victim of a repeat offense, but don't want to keep punishing someone for their past forever, either.