Well I'm not any of the ones you asked for help from, but I do feel for your sitch.
IMHO it is a classic and very destructive MLC. Backing up a bit. What were her issues with you? Were there problems in the M that might have triggered the MLC aside from the mom's health problems? She mentioned that she felt she was doing most of the work in the M, how true was that?
Right now there's nothing you can do to change her mind about anything. Protect yourself and your kids. Get a lawyer and a T for your D. Get close to them like you never had before.
The MLC spouse is like a tornado hell bent on destroying everything in its path. You need to grab the kids and barricade yourself in the storm shelter while she's raging.
If this is an MLC, you're going to need two things: Prayer and Patience.
As a spouse of someone in MLC, you have only two choices:
1) Cut your losses and leave - it will get a whole lot worse before it gets better.
2) Stay - but be prepared for a constant up and down emotional roller coaster ride that you will never believe. Plus MLCs can last between 2 - 5 years or more, so you are going to need patience and compassion beyond belief. You will have to GAL and live your life without her in it yet live with the hope that she snaps out of it one day. She might not.
It comes down to what do you want to do for yourself.
M-43 W-40 2D - 9 and 5
Emotion, yet peace. Ignorance, yet knowledge. Passion, yet serenity. Chaos, yet harmony. Death, yet a new life.