I'm not sure why you have to tell the girls anything at this point. As you say, your w ended the m, you are merely formalizing it. What's to tell? And no, I am not telling you what you should or should not do re: your m. As a Catholic, I know your dilemma and that none of us can say what we'd put up with or for how long, etc. Even div your w doesn't mean things won't ultimately work out. Imho, the only chance you have of getting anywhere with her, little as it MAY be, is by moving on, whatever that means.
If this last post of yours sticks with you and you don't revert back to black and white thinking/judging, then you have indeed learned something valuable.
I wish the priest had been more helpful. I found one who was and that did ease my mind, along with the inner knowledge & conviction that God does indeed want us to be happy. He does not want us to suffer endlessly when another person makes bad choices. But it is up to US to not let other's choices decide our fate, and it is up to us to determine our own happiness levels.
Good luck, j-
M: 57 H: 60 M: 35 yrs S30,D28,D19 H off to Alaska 2006 Recon 7/07- 8/08 *2016* X = "ALASKA 2.0" GROUND HOG DAY I File D 10/16 OW DIV 2/26/2018 X marries OW 5/2016