This whole thread hurts because it sounds so much like Cricket and I. I wanted so badly for things to work out. IT took me some time to get over the betrayal, but afterwards, I wanted all to be happpy. We have had about 2 months of peace in a year of drama and stress.
I will not claim to understand her, that is one thing I have never been able to do. She's lied, accused me of verbal attacks (and while yes I am guilty of a few, not everything I say is about her, contrary to what she believes), played games with my husbands heart and it has really all fallen apart.
For whatever reason he still loves her, but I as far as I am concerned she doesn't exist.
All that being said, I would like for you to have a better outcome than I did. But it depends on the three of you. Poly is all about honesty and balance. No one person can do all the work.
I think you all need to take some time to heal from all the pain caused, and at that point decide where things go. This is not going to be all happy and wonderful unless you are all on the same page.
I still believe in poly. I still believe it can be successful. Even after an affair. I think had honesty (both to ourselves and the others) and care been a little more important in our V, things would have been different. It's not the poly after an affair that was wrong, it's the people involved.
Only you know what you want/need, same for your husband and his oso. You all have to verbalize those needs in order for this to workout in anyway.
The best advice I have for all three of you is time, honesty, and healing.