I really related to what you expressed about your own experience of divorce. This made me suicidal, not kidding.
My step-dad said something that really helped with this...how blessed my children are to have someone who can empathize and really be here for them. I cannot control their dad's behavior but I can be their rock. I can relate to them and help them in a way someone else could not.
It is little consolation but it helps and I remember it often.
I have been through the "conversation" and I survived (barely). H moved out and we're still breathing. The kids are hurting and confused and I'm still here mothering and handling it.
Coach says you can "handle it"...he said it to me and I answered in my mind "no I can't dammit, you don't understand." Guess what? I CAN handle it and I am!
There is no holy grail. There is no lifeline sometimes to help you make what feel like million dollar decisions (how to respond to x, what do I do about y)...eventually, when you are detached, you know what to do and if you "screw up" you don't sweat it because, hey, per Thinker, what is the worst she can do? Divorce you????
Do you see the freedom there? Tell me because I will back up and break it down if you don't.