I tried to explain to my daughter that's because of me, not her, but the kids are looking at it as we are all her victims.
I've been trying to sneak in a reply for quiet a while. I think you've touched on this in several places.
I know as spouses, we weren't perfect, nobody was.. but did you disappear for days, night and hours? Did you yell and scream at everyone telling them, they made you miserable and you deserve whatever it is you're doing?
I know the answer is the no. In no way did anything you do, justify what is going on. I know in your heart of hearts, you blame you (which you shouldn't, I know, easier said then done) but to your kids, you should kindly place the blame where it belongs, on your W. Your daughter is right, you're all victims and as an adult, you can deal with this, get your bearings and move on, but to you kids, they are 10 times the victims you'll ever be.
I think when I realized that, I found my strength. It took a while, I won't lie, but a mature, solid person who loves you and respects you, wouldn't be doing this and they wouldn't be dragging the kids through it either. Sure, things don't work out, but you try, honestly, to fix things and go through due process and save the kids from what collateral damage you can.
At this point though, it's an MLC and it's an all out war that's on your shoulders to be stable and pass that on to your kids.
It's hard not to care, not to comb through everything and find some little thing that could have been changed to prevent all of this and the truth is, it doesn't exist. Two people have to want to fix or have the relationship. You held firm on your end, she went off the rails. It's her, not you.
Depending on how old your kids are, I would be honest with them and not shield them from the truth. I would be neutral in tone, simplify just give them the facts and allow them to explore their feelings with you and respect and validate any decision or feelings they have. It's not your job to protect both them and their mom from each other. But you need to be the role model too and not bad mouth your W.
It was important to me that my son was allowed to see things as they are and that he was allowed to develop his own thoughts and feelings and that i also respected them. Like you said though, kids are smart and they already have it figured out. it will be worse later for them to find out you lied to them (even if you thought it was in their best interests), because right now, everything is lies and betrayal to both you and them.
That's just my opinion, take it or leave it, but at the least, please don't say "it's because of me" either to them or yourself, because it simply isn't true.