You've been asking about your STBXB's family and their morality.
My answer: They are a moral cesspool -- plain and simple. The way of the world is darkness, death and destruction. No light dwells in their family. They are accursed. I'm not joking. There is such a thing as generational sin and broken-ness passed down in families. It's hard to break. They have to work hard at being decent. Doing the wrong thing comes natural to them.
You lament the loss of your daughter.
My response: What does your lawyer say about limiting your daughter's access to OW now and to limiting your husband's access after the divorce? You should move to my state, you would tak him to the cleaners and he'd get your daughter every other weekend. My guess if your STBXH and the slutty OW and his immoral in-laws are who you say they are, they SHOULD'NT get access to your daughter so easily. You seem resigned to that in a way that surprises me. Is it inevitable that you split time with daughter 50/50? Isn't their a better lawyer than that in your fair city?