Welcome Middy, glad you've found this thread, you're definitely not on your own here. Please do keep posting, sometimes seeing things in print makes it clearer, and of course you'll get lots of kind words of support too.
She makes it all about her and I feel like I have to protect myself by not even engaging. Apty this is where I'm at too. It's so exhausting having to deal with all this without having a mum to truly rely on, isn't it? Do you have friends that you have confided in, who can scoop you up? Or can you get a break away from the DCs for a few hours just to rest and/or clear your head? You are probably much stronger than you think, but you do need to take care of yourself while you're dealing with all the pressure.
As for my own toxic mother - we live in the same town, and I used to rely on her quite heavily for childcare, but haven't been able to dicsuss my feelings with her ever. Then she started her toxic nonsense on DD when she was in her care, so I put a stop to that too. I only see her for short bursts of time now, and I am very quick to call her on any rudeness (it has taken me years to be able to stand up to her like that). I have to work hard to stay "adult" with her when I do see her, but it's definitely worth it.
I think I have mentioned on this thread before, that the one thing that has helped me deal with my mother and how she has brought me up (and how that has impacted every relationship decision I've ever made) was a therapy called BodyTalk. In one session my mum featured really strongly (and in another session my dad featured very strongly as her enabler) and since that day, I have felt free of her shackles. It still hurts hugely that she cannot support me in the way other mums support their daughters, but I am no longer hamstrung by her beliefs or what she will think of me. I am just quietly accepting of the fact that she cannot support me, and gets some satisfaction from criticising me. It's her problem. I'd really recommend BodyTalk to anyone. No idea how it works - but it does! There's a website with a list of practitioners on it.
In other news, I had a complete wobble last night after my appointment with the solicitor. I just felt that she didn't have any concrete advice for me, and she was very gloomy about H's chances of buying me out (apparently mortgages for this kind of thing are like hen's teeth just now). Interestingly though, even though I was very low, every time I thought about giving in and just not doing this whole separation thing, I was filled with dread.
So I had an early night, and woke this morning with renewed determination to stay positive and keep pressing on with plans. So now have a shiny new current account in my own name, have started to transfer some bits and pieces into my name only, have called up for a benefits application pack. Onwards :).