This has to suck as it seems you may be the only one that is or is willing to put the effort into this to salvage anything.
If neither of you two crossed that line, one can only assume she has some knight in shining armor swaying her decision.
I’m sorry to read this and i can’t imagine the pain...
This is honestly a great question. I would use every last resource before splitting up with 4 kids. There's a lot of things that a go between could resolve that the 2 of you can't.