I woke up tonight and your situation was really on my mind.Something Stronger had said to someone else was percolating in the back of my mind...she'd asked someone else if he could be her W's white knight. I thought OM was the white knight, that he was going to rescue me from my suffering...but he was a wolf in sheep's clothing.
I know it is a lot to ask someone to endure the OM situation..but the wolf is at the door, tristan. She's a fragile person right now.. please think long and hard about pushing her out, towards him. He is telling her you don't really love her, that you never loved her, that you don't know how. Proving this wrong doesn't make you weak, or spineless. There is a difference between self-respect and "pride" the kind of pride that cuts off its nose to spite its face.
Time is on your side.Only you know how much you can take, but I would plead with you to take the longer view, bide your time, to get support for yourself, and at least for the moment, try to protect her from herself. That is NOT a long term solution, and I don't mean it as such...but divorce is permanent. One thing that stuck out in my memory from Michele's book is...you can always get divorced later. You can always make an ultimatum, you can always ask her to leave, but you don't have much to lose by continuing to show her the real person you can be now, when she's in your home. You bailed on her the first time when you quit marriage counseling. Somewhere inside she expects you to bail on her again...OM is using that against you, I promise.
Some here would say, hey that's the consequences...but she's the mother of your children. What happens to her, happens to them too. You don't strike me as someone who would take any pleasure watching her fall on her face.
I would not give this advice to everyone...but I feel compelled to say this. I feel it in my bones that this woman needs your mercy right now, not tough love. Time will tell if it will work. Her problems may be too great for your marriage to bear, and I don't advocate sacrificing yourself for a lifetime for someone who can't get straightened out. But for now, try not to look at her as someone to fix, but as someone who needs your protection right now.