Amazingly crazy ex-husband, help!

[Augtan]

My story is long and complicated, but I will do my best to shorten it. I need some advise, help, whatever. I tried to do divorcebusting for several months, but it did no good because my H was back with his OW and I didn't know it the entire time I was working on doing this. Anyway, I moved with my kids 700 miles away. He still denied being with her but within days of the divorce being final he brought her out in public (just like I told him he would, and he told me he couldn't because they weren't together). So, he then continued to lie telling me they had just run into each other again a few weeks ago and were barely even dating (a few hikes, bike rides etc). Well, then, I found out from her ex-husband that they had been together since a few days after he moved out of our house 9 months before the divorce was final (just as I suspected when I lived there, many things pointed that way, but he kept lying to me and telling me he would never go back to her!!) So, for 6 months out of 9 I had lived in the same place they did and he was seeing her but hiding it all. Now, they are very serious and talking marriage. We will be seperated for a year on July 26th and divorced for 2 months!! Nothing I say or do matters and only pushes them closer together and I logically know that, but is so hard to watch someone you love do this to himself and his kids. Our kids know who she is, what she did and all about her. They want nothing to do with her, or him if he is with her, which they have that option. My problem comes when it comes to my youngest. She is severe ADHD and ODD, she is extremely impulsive. They are going to visit him for 3 weeks in a few days. Her therapist thinks it is not in her best interest to be forced to meet and be around the OW (who by the way, gave up full-custody of her only son when he was 5 yrs. old to move close to my married husband, and make it her full-time hobby to break up our marriage, which she finally did!!). My DD has said she will do very harmful things to herself in order to get away from having to meet the OW. I have tried to talk to my ex and told him to call the therapist, but he says that he will do what he wants to do and the kids will just have to deal with meeting her and he doesn't care how they feel about it at all. He says that I have put all the feelings in their head and when they meet her they can make up their own mind if they like her or not. They all have said if he forces her on them they will never go back, and that breaks my heart. Before he met this woman, he was an amazing father and husband. We had our problems, but after I found out about the affair I tried to do whatever I could to heal our marriage and he was into it for about 5 months, then gave up, he worked with her all along and I know really never gave up the fantasy of how good the affair was and that maybe they could be together and have that all the time. And, now he is doing it and wants to marry her. I am just heart-broken. He was my love since I was 18. But, all the lies he told me since he moved out has made it impossible to even co-parent with him and with her in the picture offering the continued fantasy life I cannot compete with, I don't know what to do. How can a man ever respect a woman and want to marry a woman who was sleeping with him while he was married, who gave up her own flesh and blood for no reason (she is 36 yrs. old with a great job, house etc.), who convinced him that he was in an awful marriage which in turn has made him lose his kids altogether because they now live 700 miles away. I have written a book here and there is so much more, but I just don't know how to handle him with that woman or what to do to about the fact that he is soooo snowed by such a wh**e!!

Me:38
ExH:42
K: DD-16, DS-13, DD-10
T: 20 yrs
M: 17 1/2 yrs.
Bomb1: 7/6/07 EA/PA wh**e at work
Sep.1: 9/1/07
Back Together: 12/10/07
Sep.2- 7/26/08
D filed-11/08
I moved with kids: 1/26/09
D final- 5/4/09
Bomb 2-5/6/09-told he was "dating" her again!
Bomb 3- 6/14/09-found out they had been back together since 7/27/08 at least and are very serious!!