I probably have an idea of Pup's advice. Not many times I disagree with him, but I look at it this way....what do you have to lose by holding on till after Christmas? Before you say anything, I have thought about the self-respect....and you know how strongly I feel about a W respecting her H. So, have you considered telling your W that you have decided to make the very most of this next month....for the sake of your girls. By doing so, you are not stamping your approval on her A with OM. If you want to sleep apart from her or even consider it an in-house separation....I think that should be your call from the POV of not living in an open M, instead of her her call of chosing OM over her M. Does that make sense? To me, that leaves your integridy in tack, but also buys a bit more time....if time is what you want. But most of all, it doesn't distroy Christmas for the kids.
I suppose the big question would be...what do you really want. Do you want one last shot at the M, or are you ready to call it quits? The second question would be....can you do this for the girls or not?
GW, in spite of what any of us advise....this is your life, not ours. You have to make those decisions and live with the results.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!