It sounds like your handling things well. DnJ gave you great advice and You’re doing a good job if your kids are leaning on you, keep it up.
So much of what you write is familiar. At one point, ex criticized everything I said and tried to tell me what to talk about/say to the kids while we talked on the phone too. I also know she was recording everything. I know how ridiculous it is to have to deal with this. Do your best to act as you normally would and, in my case at least, she will give up on this after awhile.
I think you did a great job listening to her and wanted to remind you not to believe all they say. I heard a lot of those things but I also heard the contrary before the mlc. When your w said she left because she feared for her life, I take that as mlc depression language for she felt like she was dying and ran.
Take care of yourself and the trio. It’s really hard that deal with irrational anger like this and you’re doing a good job!