My husband and I have been having problems for a couple of years now, but things are worse than they have ever been.
...many other have happened as well that I have looked past for the sake of our DD, because she loves her daddy so much.
I'd wondered about that, from past posts.
Looking past things for the family's sake, when BOTH partners are actively working on things, is one thing.
But looking past things just to keep everyone under the same roof, despite no changes or attempts at changing from one partner, is totally different.
Getting strong and getting out, when situations are getting scarier, is a much better idea than continuing to stay until things hit the fan and the hitting starts. Trust me. You do NOT want her earliest memories to be vague fuzzy memories of dad beating up mom. Or memories of having to run away, mom kids dogs, to a friend's house because dad has called and (que scary music)
dad is on his way over. And so on.
I second this. Do not shy away from the idea of medications - they're far more advanced than you could imagine. Ultra-modern medicines such as Tianeptine (Stablon) and Moclobemide (Manerix - you should be able to get these in the States nowadays) in particular have a high success rate with minimal - if any - side effects.
But why should she? This is situational. Her husband is having problems and is making the house miserable. If he changes, she's not miserable. If she gets out, the misery lightens. This isn't a mysterious, "why am I so sad despite my life being incredibly good", depression. This is based on something. IMO, to medicate now would be to deaden her sense of danger, and might lead to complacency, and might lead to very bad things.
So I said fine, I am going into work. Well, that upset my DD really badly. She starts crying for me to stay with her and not go to work. I try to console her and tell her I will be back soon, but mommy has to get ready to leave. She is hysterical and I feel awful. My DH then storms up out of the bed and says to me - you obviously dont want to deal with our daughter today, so you are going to work!

I told him that didnt even make sense - but he loves to turn things around on me. I told him no, I gave him a chance to get up and look for work, he chose not to, so I had to go in. One of us at least has to work. He then takes a sippy cup off the table and throws it at my face. It missed, but that was it.
Her hysteria is because she just doesn't understand. Very common. I would get so confused I would side with my dad! So she's hearing and watching, and *feeling* all of this, and she's confused and acting out. And obviously the idea of being alone with dad and the weirdness he probably puts out isn't making her happy, so you going to work was the breaking point.
Glad you got out for the day.
Thank you all so much for your support. Isnt it funny that total strangers can be the voice of reason and really help sometimes?
I feel bad for my beautiful and wonderful DD that she isnt going to get the chance to have a happy family. And I am mad at him for that. I know it doesnt have to be permanent, and I really hope it isnt. But who knows at this point.....
Strangers online did more for DH and my relationship than anyone in real life. IRL people were so on the surface. People online asked the deep questions.
She'll have a happy family; happier than it is right now! If this spurs your husband to take care of himself and you guys can be together, it'll be happier. If your husband takes care of himself but you can't be together, it'll be happier. If your husband continues down this track and you can't be together, it'll still be happier.
It won't be mom+dad+kid, but if that combo is unhappy and volatile and a spouse won't work to change, it will be happier to be away.
You may also want to let your local constable know about the violence/lack of meds. It is good to have documented; they also may be able to help you "force" him into a facility.
Good idea. Also it could keep him from having alone time with her until he gets more stable.
Good luck. You're doing well. Ultimately, your girl will be stronger than if you just stayed and let things be and lived in misery and confusion and anxiety.