aver, I think until you detach and/or move away you're going to be hung up on X with OW no matter the outcome of the house. I know what it's like to cringe at the thought of having your partner move some OW into your life. I told BF that's what hurt the most, feeling like I was replaceable.
I started out DBing thinking that there was no way I was going to let some whore steal my man and my life. When the switch flipped I decided that if she wanted a cheating, lying coward then she was welcome to him because I deserve MUCH better than that. I love my house. I liked my life. But the house is just a thing and my future looked so much brighter on my own that I was willing to just walk away (not without fair compensation).
This is why it is important to figure out what you want your future to look like. Of course I think you should work to get the best possible financial outcome because honestly that's all that's left. Just make sure you're not holding onto a thing (house) for the wrong reasons. Yes, it's a slap in the face to move OW into your home. But if you're not there to experience it, is it really a slap?
Don't cut off your nose to spite your face (and all those other trite sayings). Focus on doing what is right and best for YOU.
My two cents on the intervention is that it would be a waste of time. I exposed BF's A to his best friend (S) and best friend's wife (A). S's response to BF was that it wasn't smart to screw someone at work because that could mess up his career. He said nothing about me which hurt a lot because S and I used to be coworkers and had a friendship independent of BF. A is a very outspoken and opinionated woman. I have never known her to hold back. She told me that she was going to read BF the riot act when he came to visit them and she would not forgive him for what he had done. Turns out she never said a peep to BF. She told me later that I seemed to be fine with it (at this time we had split up) so she didn't pursue it.
So even if you ask X's friends to talk to him (which is controlling others, not yourself) it may not have the results you want. Are you 100% certain they are on your side and would agree to talk to X on your behalf? They could tell X that you're sad, pathetic, begging for more time in order to win him back, etc.
The only way I see this working for you would be to able to slip into a conversation the fact that X was going back on his word to wait a year and that if he wants to play hardball then you're willing to do that to stand up for yourself.
But I will wait and see what others have to say on the subject.
If you love somebody, set them free. http://tinyurl.com/2empx2g