You have been so supportive of your H during his difficulties with S16 and look where it got you .... nowhere! Now you know where you stand, Alison. Your H thinks you a fool .... he manipulates you into being a responsible parent, while he is just getting what he wants out of you. Then, he stabs you in your back. Don't feel bad for supporting him though ... you were doing this for your S16. I agree that, perhaps, you should let your D13 decide, but for her bad behaviour there should be consequences. She will not do as told, but there must be something she holds dear, i.e. her cell phone. Take it away for a time until she conforms. If this doesn't do it, then perhaps it's time for her father to deal with her and she can see how 'wonderful' it is there with OW where she will have to compete for her father's affection and love. At least you've had the best part of their childhood ... treasure those memories and let him deal with the crappiest part of their childhood (the teen stage) and eventually after all that, they will come back to you .... believe it. In the meantime, live your life. Live YOUR life.
Just some thoughts, and not sure how much this will help. Your STBXH is a fool by responding like this. He is only damaging his own children ... and for what? You can play his own game and let the kids know why he truly wants them at his home .... so he pays less money for their upkeep (but, I know you won't do this because you really care about them ... I think they will figure this out themselves eventually ... although, he is probably telling all kinds of lies about you, so maybe it's time to defend yourself). Not because he has undying affection for them ... he proved that by breaking up his family.
Don't cling to your house ... I am learning in my own sitch that there is no emotional value in stuff, even a house. If you have to, sell it, pay him his money, and find somewhere where you don't have to associate memories of your family. Life is different now ... let go of the past ... move on. Life is too short. Still, I know how you must feel.
Take care.
Me:57 H:52 M:28 Got another lawyer last year and filed. D35,S/D twins28,D22 EA4/04 End? Who knows? "Life is like a mirror. Smile at it and it smiles back at you." — Peace Pilgrim