Its not that hard to ignore someone. Simply dont reply to messages and don't answer the phone. Quickly they get the hint. If he was smart ge would have a restraining order on her and call the cops with any attempt of contact.
On top of that, I dont think id be friends with him or even considering being in a relationship with him. Why was he dating a meth head? Most times it would be because he was into that crap, too. If he could have a drug problem he could be a serious danger to your child.
Sounds like he has a lot to do to straighten out his life.... Before even considering anything else.