I understand completely. S3 also acts out attacking me especially when I side with H. But like you I constantly reassure him that I will always be there for him and that I will never leave him.
A while back S3 had a crying spell because of H. I told him that it is okay to cry but if someone did not care that they hurt you do not let them see you cry. H was furious. I don't speak ill of him in front of S3 but I have to be honest and admit that I have lost it sometimes when he leaves and S3 is crying or asking him if he is coming right back. (H's new leaving words since S3 realized he "ever come back").
I have told him that daddy does not want to be here, though the last time I modified it to say with mommy since H now says that S3 is innocent and I am the hindrance to his happiness (H says he left because I neglected him for the baby who "broke up a happy home". And of course it had nothing to do with Ow.) H has also said that if Ow were not in picture he would not come back but I seriously doubt that. He tells me that he only comes to the house because S3 but if that were the case he should be here a lot less especially when S3 is not home. H still comes by so are you here only for S3 or what? I must admit for the last 3 months he seems to be more drawn to Ow (ultimatums have been put in place). Also has not happened for two months, the longest time since A began in Mar 2004 and he moved out in August 2004. And I have to be honest, I'm really missing it right now.
If H thinks me not being a part of his life is going to help him be happy that is a laugh and half. That just shows how delusionsal he his about his fantasy life right now. No crying S3 when he wants to sleep, house always spotless, no bills to pay (she pays them all), no hot cooked three square meals (she thinks it is beneath her to cook so he eats with us ALL the time) etc. They bad will come there too. And no food? Then what? Ow2? Maybe H thinks that LBS would be willing to be OW?
My H and Ow classify their finding each other while married to other people as "things happen that you have no control over". The nerve of them. Grow up face your problems and fix them. That is reality, not this delusional fantasy world where you have found true love and left behind nothing but destruction to pursue it? Do you really think that you are going to find happiness after that?
Think again. As I say to H, "God makes ugly but he sure does not like it." Ow needs to think about that when she refuses to miss Mass any Sunday. (laughable isn't it. I call it playing with God.) In fact Ow gave H a rosary to hang in our vehicle (when he still lived at home) as a protector???? I am a practicing Catholic but WTF???? You do know that it was quickly removed or it would have been tossed out the window.
If H were depressed and medicated like your H I don't know if I would have been able to handle all this. He is bad enough sane.
I've said all this to let you know that someone is right there with you, continue detaching taking it one day at a time and hang in there.