Nine - You and I are in much the same spot right now. Our STBX's are openly involved with OM and not even hiding it from our children. That's how right they believe they are. They believe whole heartedly that they deserve this happiness.
We really do have only one choice - to detach, go dark, LRT - whatever you want to call it. But you and I, also have one thing is common, we simply don't want that choice. We hate feeling that we are stuck in a corner that we didn't choose. Still, that is the reality and somehow we have to move forward. Even as I type this, I don't know exactly how to do so, but I also know, that some day we will be whole again. We deserve that.