I can only reiterate what others have said.
Please help to get her some good legal advice. Although I thought so at the time, my solicitor wasn't much good and she let me get stung for thousands and my children too. Your DD needs to stop agreeing to whatever he wants, he will take her to the cleaners otherwise and to put her and her children's needs first. I know this is difficult at this time. You feel in a sort of limbo and a dream and as if it's all not real. Go with her to any appointment, take a note pad, jot down what they say. Do what you can for the day and then put it to bed, so to speak, and help each other relax.
Get any child care arrangements in an order or a contract. He cannot just say he is not having them after making arrangements. If he is doing this now what will he be like in years to come. Get it legalised. My son is currently having counselling because his father abandoned him at 8 years old, he is now 17 and it still hurts him deeply.
As for the CSA, I know that for one child it is 15% of the man's wage. For two children it is 20%. I don't know what it is above this for more children.
My ex asked me to sign our marital home over to him in exchange for all our debts. I agreed. (I moved into council as he was violent). We got to court, his solicitor said the house was in negative equity, more or less made me sign the house over and then only agreed to pay debts in joint names. My personal debts were handed back to me. He sold the house two months later at a profit of £60,000. So I missed out on £30,000 and my debts being paid. How someone could be like this when you have shared a life and had children is beyond me. This was in 2001.
Take care of yourself Kitty we are all here for you, anytime.