Hi OP, I left an increasingly toxic and EA LTR with two kids (together 21 years since the age of 17). I had been thinking about leaving for nearly 2 years so thought I had got my head around it.
I found a little rental place and moved out with the kids 4 days after telling him (the 4 days were hell). I had already set up another bank account, arranged for work to pay into that and changed my personal direct debits etc. In the first week I lost a purse with 300 quid cash in and all my cards, and I hit another parked car whilst going to the bank to cancel my cards. I was a mess for atleast 2 months. I felt like it was a dream, I was on auto pilot. I focused purely on me and the kids and trying to get by hour by hour. I was an emotional wreck even though I knew it was the right thing to do.
The hardest thing of all was managing the preceived guilt I had, and trying to keep him at arms length whilst dealing with his poor mental health (for the sake of the kids). I cried almost every day for atleast 4 or 5 months.
However I would like to say almost 2 years on, i am in a new house I rennovated, I have new friends, I am seeing someone, I have freedom and the kids are really happy. Ex has started to see someone and we have turned a corner. I couldn;t go no contact with him as we are selling a house and the kids, and even though I hated him for what he did, i still cared about him and wanted him to be ok. That was the hardest part for me, not being alone, but his behaviour and stress. Its still a type of bereavement, no matter how bad things have gotten, you still lament on the past.
What helped me was talking to friends, jounralling and exercising. For almost a year I kind of hibernated, just going at my own pace. Good luck, its tough but so worth it!