I am sorry things are so hard right now.
You don't have to be friends with that guy. Tell him firmly but politely that you do not want to be friends. It's okay to try and aviod people you are uncomfortable with. Be nice, but not overly friendly. To lead him on would be worse than to totally cut him off.
I understand that you SI'd to cope with difficult and overwhelming situations, but please be careful. The more you do it, the harder it is to stop.
Please take care of yourself.