Hi Eve44,
I am so sorry you are going through this and want you to know you aren't alone.
About your eldest daughter... .My son (now 15) went through an almost identical descent into depression and anxiety. His struggles started to manifest at age 8 when he told me he didn't want to live I didn't even know a child that young could feel depressed.
Like your H, my son's father said similar, unbelievably abusive and traumatizing things. Like you, I have carried a lot of guilt about keeping my son in that environment for so long. The good news is that you are doing the right thing by leaving, and by getting your D into therapy this early.
Learn everything you can about validation and start using it with your D11. The benefits will be both immediate and long-term. More than anything, she needs to unload these feelings and have you bear witness to how she feels -- this is an important part of helping her learn to
build emotional resilience. It will feel counter-intuitive at first, and emotionally very difficult, but ask her how she feels when her dad says those things. When she says she doesn't want to live, validate how she feels: "You must be feeling so much pain. I can tell that daddy has hurt your feelings with what he says." Let her express her sadness even if it feels you will break inside With my son, I think the thing that broke him was only partly what his dad said. The other part was feeling unheard about the depths of his sadness. He needed a sympathetic witness. Instead, I comforted him with platitudes that did not allow him to discharge powerful feelings. That made him feel alone, and he felt like he was "not good" at pleasing me, who seemed to want him to feel better about himself when he wasn't capable of doing that just yet.
I learned to also call out the bullying for what it was. "When daddy does that, he is being a bully. There is no excuse for bullying. I am the adult, so I'm going to figure out how to handle this. It might take me some time to come up with a solution, in the meantime, let's have a time each day where we check in and hug each other and let all the feels out." Or whatever sounds best to you.
About the divorce process: my advice is to start by asking for full custody if you think that is best. The way to
manage the fight (avoiding a fight is probably not realistic at this point) is to be assertive, and that means doing what you think is best and sticking to it. You don't have to be aggressive, altho for many of us, assertiveness feels aggressive when we first start turning the ship around.
My ex husband was a former trial lawyer and I felt dread like I've never experienced before. During my custody battle I was a graduate student and full-time employee not making a whole lot of money. It took a while (these high-conflict divorces are marathons, not sprints), but I ended up with full custody of my son even tho many people said it was not likely, including my lawyer.
The key to doing well in these divorces is to ask for what you think is best -- don't worry what the lawyers say -- and then propose solutions that demonstrate you have faith your husband can become a good parent. That's what court cares about, that you, the problem-solving parent, can protect your kids while giving their father a chance to become a better dad.
Remember to take care of yourself, too. I know it's hard to do when you have young children and this major BS going on around you, but you are stronger than you know and can make it through this.
LnL