Great job U turn. You at least stood up for your beliefs and weren't afraid of her reaction. That's all you can do, and pretty impressive for month 4.
As for her, there is a reason she won't see eye to eye on what's fair. I don't know if you followed my last thread, but I had some interesting discussion about addiction and needs. I was saying when we have needs not being met, they really create powerful longings in us. When we find behavior that seems to meet those needs it is overpoweringly desirable. And since we believe ourselves to be good people, it's easy to rationalize our behavior. IE, I have emotional needs, you couldn't/wouldn't meet those needs, therefor it's your fault I had to go elsewhere, and whatever consequences occur from this new fulfilling relationship are really because you're defective. That's her stance. So to her, it is unfair that she should be inconvenienced because you failed her as an H.
Will that ever change? I could speculate that at some point when the new relationship breaks down and doesn't meet her needs she may bottom out, and at that point there is a chance that she finds healthier ways to do so, and at that point she may realize that it wasn't all your doing, that maybe she could've found a way to meet her needs without destroying her M. But that's a lot of speculation. The fact is that there are many alcoholics that die alcoholics, many lung cancer patients that smoke all the way to the grave, and so on. It's not a good idea to tether your happiness in life to someone else's ability to grow...in fact, that would be the opposite of growing yourself. Best to just have a moment of silence for your lost marriage and then keep moving on and letting go.
So in light of that- what can you do with a W that is in an open affair, insists that it's over forever, but refuses to move? I'd say put some time on the clock- maybe 6 months- and decide to detach, let her go, and leave the M behind. Do what you'd do if you were single with a roommate, and get yourself to a state of acceptance about your D. If in 6 months you have moved on and are truly at peace, in a positive spot for yourself, and she's still doing the same things...at that point you may decide to file yourself, move out and take your kids with you (at least half the time), and/or other necessary actions. But there is no hurry if you are detached. If you can't stomach the current situation that just means there is more detachment/growing/healing to do on your end (which there is), and you can do that in your home as easily as in another believe it or not.
And if you decide to give it some time, odds are that things will change before then. She might decide to move in with OM in two months, or they might break it off in three, or she might file on her own and try to evict you by falsifying abuse and filing charges, who the heck knows...but I don't think you'll ever regret looking back and knowing that you didn't make lifelong decisions for your family out of pain and reaction. I know 6 months of this sounds impossible, but it's not a lifetime, and there are things more important than your own immediate discomfort. As I said, one of them is getting to a point that it's not so disturbing because you have transcended the situation by working through the loss and dealing with the emotions that come from it.
So keep posting, keep reading, keep GAL, and start rebuilding the life you'd rebuild if she died, only right there in the same residence.
Good luck U!
Me:38 XW:38 T:11 years M:8 years Kids: S14, D11, D7 BD/Move out day: 6/17/14, D final Dec 15