If there weren't a child involved, I'd say, sure, go for it if you want. The only person you might be hurting would be yourself. However, with a child involved, my advice is to let this guy go. Lots of us love people we know aren't good for us and we can't be in a relationship with. It isn't the end of the world and there is love out there for you that isn't toxic. You won't find it though, if you keep hanging onto this guy.