There is a high caloric liquid that I use called Dyne. I like it much better than nutri stat and it is very palatable and the dogs actually love it.
Although coccidia can be caused by stress and a new home that baby should have never left that breeder at 15 ounces.
I don't let my babies go now until they are 2#. No matter how long that takes. I normally do not have babies that size but if and when it happens they stay here until they are 2# and have had no problems.
Best of luck to you and your baby. I think small claims court is your best bet!