I believe it all comes down to is I may know too much about the A. And it's something I can't get away from right now.
It looks that way right now. I get it. I can tell you that it does get better. Sadly the truth is it may haunt you for a little while.
Right now knowing too much about her A seems like a curse (and it is, don't misread me), but the alternative is that you don't know anything and your imagination put horrible images in your head. That sucks too.
I guess I am trying to say (and doing a horrible job of it) all you have to do tomorrow is to decide, not to decide. Working things out isn't a destination it is a path. You can leave that path whenever you want.
You can try. Not for you, not for your W, but for your Daughter. If I read your post right, she is worth the risk, right ?
I had D papers in the works, had found an apartment to move to, was shopping for furnishings, etc. When it came time to tell my daughter that Daddy was going to move out and that I was going to D her mother. Well, it broke me. I couldn't do it.
I took that as a sign I had to at least try. I still tear up now thinking about her and how she may have reacted. So many days after that I needed strength and I found it when I looked at her and how happy and smiley she was when I had planned on telling her.
With her in mind I found great resolve. She gave me a lot of hugs, "just because," but I found the strength I needed at the time there. Look there, I think you will find it.
I can also relate to family of origin and trying to not place that hell on my children.
The reasons can change later, but worry about later when later gets here. Day to day is probably all you can manage. That is OK. Trust me when I say this gets better. If you take nothing else from my post, just take that. No matter how your M ends up, this does get better.