I think you have been swallowing lots of pain this last year. Be careful, you might end up defining yourself by being the person that swallows pain so everyone else can be happy.
What do I mean?
1. His parents. Why are you so concerned about making them feel uncomfortable? Blood is thicker than water, but, perhaps that's the problem. You H is surrounded by people who seem to act as if nothing's happened. Tell them the truth, the whole truth. Tell them you want the marriage restored, but you husband will have none of that. Tell them about both affairs. Tell it to them once, and then leave it at that. Say your peace.
2. Your daughters. How will they develop a moral compass if everyone is playing the "I'm OK, your OK" game? You husband abandoned his family and has had two affairs. That woman is not his girlfriend, she's his mistress/OW. She's probably so damaged, she doesn't care who she hurts in order to get some comfort in this life. I think you need to sit them down and your kids them that what their father is doing is wrong, as is the relationship with the OW. It's called adultery. You can also tell them that he's their dad and they can love him, even when he does wrong things.
Your daughters want more time with him to "make up" for the loss. They are trying to stoke the fires of love with a parent they feel has abandoned them.
3. Custody. Perhaps seeing their dad and his mistress 50% ff the time might not be best thing for your daughters, even if they think it's a good idea. How about every other weekend, alternate holidays and some summer vacation. Being a mom means taking your daughter's best interests at heart, even if it means crossing their wills.
I'm sorry this hurts. But I'm not exactly sure what your DB strategy was, except to save yourself. And that's fine. Part of saving yourself in not simply "detaching" from your H and having fun yourself. Part of saving yourself is valuing yourself enough to set up healthy boundaries around yourself AND your daughters. Pretending everything is OK and not asking people to take sides is noble -- but, in the end, it doesn't help to pretend what your husband has done isn't sh*tty and morally rephehensible.
I'm speaking to you about this, because in my own situation, the major compenent of my "getting a life" is rebuilding my self-respect.
