Mighty - I think you handled it reasonably well. While it can be a mistake to get sucked into too much of their craziness, it's also important that you nip some of this nonsense in the bud by making it clear that you are not badmouthing him to the kids and that his issues with the kids are his to solve.
Also, I know this is all so crazy fresh and sudden for you, and the need for resolution is great. I know in the short term, you'd like to see him suffer like you have. Truth be told, he probably has.
In the long run, galling though it is, you will probably prefer that he be happy. After all, you truly loved this man, enough to wish him happiness even if it's not with you. Odds are he won't find it where he is now, but even if he does, it's NOT a reflection on you.
I'm fortunate, my ex's new wife was not the OW.....although, as an Asian chick young enough to be his daughter, she is the archetype that he left me for.
I'm grateful my kids didn't have to deal with a string of inappropriate girlfriends, or potentially worse choices. I'm glad my ex isn't suicidally depressed or a burden on my kids. I know I got the best years my ex had to offer, and now that I've experienced the love of a man who cherishes everything about me, I would never settle for my ex again.
So I guess what I'm saying is, stick to the high road. Don't speak negatively of your ex with the kids, for THEIR sake. And make it clear to your ex that you're not doing that, so he can't weasel out of responsibility for his actions. Then minimize your contact as much as possible.
