You are determined not to behave like an adult, aren't you.
You say your priority is to help your DD. Right. Go to a counsellor with her and state that. Listen honestly to what comes out of that. Put her first. You only have a few chances left with her in all probability.
There is nothing my children could do - but nothing that would cause me to have your attitude towards them. Yes, I might feel deeply hurt or traumatised. But I would still know it was meant to be all about them - I signed up for it, they didn't. I've been around a long time, they haven't. They'll still be living with the consequences of what I do in thirty years - I have less of my life to be affected by it. They'll be bringing up their own children and will need memories of how to do it right. Any marriage that can only survive by focusing endlessly on the adults at the expense of the children isn't a marriage that I'd want to be in.
If only you were half as interested in accessing appropriate help for your DD as you are for your DH.
Your DH sounds bitter and like he's looking for someone to blame. These are his problems. How he has reacted emotionally to the events in your family are perhaps not his fault but they are certainly not your children's fault. You have on other threads admitted that your DD suffered as a result of undiagnosed medical issues with her brother. Yet there are no ongoing allowances made for what must have been a very traumatic time for her, only everlasting blame that she is responsible for fucking up her father. Who can't go to the doctor because apparently he would never forgive you all for driving him to it, so she is grounded instead because that will give him satisfaction. You couldn't make it up!
Yes, I'm judging alright. Like many posters here, I'm appalled that there are parents like this in the world. Your DD's welfare clearly comes a very distant second to patching up a marriage with a bitter man who doesn't want to be appeased or take responsibility for himself, and who is, if anything, more troubled when he is out of the family home anyway. So she's not even the issue.
Go ahead, knock yourself out. You all seem to be on a mission to screw each other up. I just hope your DD makes it out in time.