You have done so well, have been so patient, been so caring... it is easy to see why you'd be angry with your H. You have EVERY RIGHT to be angry and hurt. You are normal, he isn't. Things being what they are, (crazy) it is probably best if you don't vent all over him... although, it would probably feel really good about now.
Leave him be, vent here, or vent in an email to me, I do understand. You MUST take care of yourself, and this means you need to process your feelings, even the angry ones. Get them out... go for a walk, scream at the top of your lungs... find a kick bag or boxing bag and beat the tar out of it... you deserve it. You have to feel or process it in order to let go of it, for it WILL eat you up inside.... trust me, I've done it myself, and it doesn't feel good, and it will bring you down too. So, get it out.
As for D4, she's being a typical 4 year old. I thought someone came down and exchanged my two at the age of 4. I didn't have terrible 2s, 3s were fantastic, but 4.. OMG, I thought I'd go nuts before they both were 5. Of course, my two are a year apart, so I had 2 years of age 4.
Let him deal with her, if he is in the house. If he messes up, wait until they come home, and talk with her about the situation... but give him first shot, so he can see what his beautiful daughter is going through. Allow him to try to be "the grown-up" and responsible for what he is doing to them both. He doesn't have them for all that long, so you can make the necessary repairs when they come back, after he is gone.
As for who she will be when she grows up, she will be wise, wonderful, and caring, because she has YOU as her Mother. Don't borrow trouble,(from the future) we all have enough going on in today, so it's best to worry about what is going on today.
Take care of you, God Bless
Love,
Laughing
Jeremiah 29:11 For I know the plans I have for you.........