I'm sorry to hear this. I agree with the others, at some point it just becomes that the minimum is not sustainable long term.
I posted in D/S the message my STBXH wrote me the other day, I think likely similar to your WW, this is part of the message.
"....I'm sorry, I would have given anything to change it. I wanted more than anything to be there for you especially after everything, but it just doesn't work for me. I can't pretend something is that isn't. ... You deserved much more than you ever got from me. ... I'm trying to do the best I can for you now..."
Really, it's not that my STBXH is terrible, he simply cannot do heavy lifting. I don't think he's capable of it emotionally. He'd proclaim he loved me and wanted a life with me, but then would do 50%-75% and I'd have hope (after I repeatedly told him what to do) but it would never be finalized. And he wouldn't even understand why it wasn't 100%, as it was enough in his mind. Then I'd question if I was off base and expecting too much.
I am just realizing now that my entire relationship with him was rooted in my hope that he'd finally see what I thought he could be, if he just tried a slight bit more. And as long as I carried us, didn't ask for much, and convinced myself to lower my own expectations, then things were okay. After 10 years in the relationship, my expectations were at ground level, and I didn't even notice until the A bomb exploded and people started asking me why I felt it was okay to be last in my own life (and I had no answer).
I know how you feel about not wanting the divorce but needing it for peace to move forward. That's where I am still, at nearly the 2 year mark.
I hope this brings you peace in the future. My best wishes for you and your children.