IF she DOES get to the point of walking out the door :
I will be honoring my commitment to you as a husband and a father. I will hold you to yours as well. We aren't divorced, I am just protecting our children from this affair until you divorce me and your children or choose to rebuild a broken family and spare these children a lot of pain... Whichever you choose first. They should not be exposed to this affair of yours. If that means you have to leave your children and your home to learn that your commitments transcend how you feel right now then that's a tragedy I will have to stomach. I do love you.
She will likely spit on it, but you need to make it clear that if she walks out that door and goes near OM she is cheating and you do NOT condone it and WILL EXPOSE IT.
I suspect it won't come to this... I think once she realizes the OM isn't stable and you mean business she will change her tune... STICK TO YOUR BASELINE I put above for you.
