sorry to butt in. Someone told me you and I were in a similar situation, staying in a miserable marriage to keep the spouse from remarrying worse. Here is a quote from an email I sent my FWH yesterday:
"We can try to continue to keep this marriage together and I can look the other way at all of your indiscretions, but once it starts to spill over into my day-to-day, I�m not going to be able to react calmly. Given the huge amount of sh-t-sandwich each of us has to swallow, any perceived effort to hand more of the sandwich to me will not be met well.
We can stay together to keep you from remarrying a teenager and to keep me from shacking up with some drunk (since that�s the way we�ll always view each other) but we both have to stay out of each other�s way."
When I read your posts, I get the feeling we are on similar paths. Good luck to you, as I cannot find a path out. Just wanted to let you know I'm thinking about your situation.

Status: Chronicled in Dr. Suess's "The Zax"