15 weeks and already picking up on the bad-man vibes from your ex? Good boy Charlie!...Just kidding. Seriously, his aversion to men may be because of your ex (he's relating all men to his first impression of
him). I'm no expert, (but I've watched a lot of them) and what I would do is teach him that men/boys can be a good thing by having them (your dad, your daughter's teen friends, etc.) greet him with a small treat. Do not have them pet him, just greet him briefly with a treat and then let Charlie go on his way. As he gets more comfortable, have some SUPERVISED petting/play time with some males then finish
that session with a treat. He will very soon get the idea that not ALL men are dogs!!
Good luck to you and keep us posted.