Julie,
He doesn't get to say "no". Get a lawyer ASAP. Get it set up in writing when and where s is supposed to be. It is wrong to just not show up when he was supposed to. H has made it clear that he doesn't have any intention to keep his word. You are your sons parent. Your husband doesn't have the right to allow a non-family member to be involved in your sons school if you don't want them to be. Ex is doing all he can to get at you and is using his own child as a weapon against his mother. To me that makes him pond scum. Get a lawyer. Get a separation agreement in place whether he wants one or not. There are consequences to his actions and one is he isn't in control of S's life without your agreement. Don't wait. Do it today and show H and OW that you aren't going to just let them get away with what they are doing. I would love to watch as he explains to a judge how he is really gay and that OW and her child are just "roommates" and "friends" and also hear what OW has to say about having the police need to be involved and how she threatened you with having her cop brother harass you. Tell the people at the school that OW is NOT on the list of people allowed to pick up your son and he is not to be allowed to go with her. It's time to get proactive at protecting your S from the crazyness that is your H! I wish I had done more and my D15 is suffering now because I didn't act sooner. You are in the right here Julie. You tried, he didn't. Don't let him hurt your S even more. Just my thoughts.....