No sweat on the hikack on my thread. We are all in this together.
First, I agree completely with what Sara, Greek ,d Karen said. They are some of the best on these bb's.
I agree also that you should not set any boundary you are not prepared to enforce. Otherwise, you look weak to your W. For me, an A IS such a boundary. I do not think I'm dealing with that in my sitch, but I can tell you there is NO way I would share my W with another man. No matter what. So, you have to decide if you are willing to share. Your fear of this stems in large part from how much self esteem you have. Saying you will share means you think either you can't do better than her or you don't think you deserve better. You CAN and DO.
I haven't read your thread completely in a few weeks, but I do not think you should move out of the house. This is her party, so SHE should be the one to find a new place. Don't make this easy on her by moving out.
If you are going to lay down the "no sharing" boundary (and I think you should), don't beat around the bush. Tell her you know, DO NOT tell her how you know, then tell her what the consequences will be if she does not abide. Then FOLOW THRU if she doesn't. You deserve and are entitled to her respect as long as you earn it.
Sorry for any typos - typing from PDA. Gonna work out then I'll check back with you. You can do this. One of those times to man up and take control of the sitch.