You need to check the provisions in the separation agreement and divorce decree. In some case they are addressed separately in some they are not. It often depends on the skill of your attorney.
Yes, but he should get the order modified to reflect this. But, this depends on state laws. In Missouri, he's required to carry the insurance, on top of his payment, so it would not affect it.
All states have child support guidelines that are based on several factors that include who provides the medical insurance. You should inquire at the court with jurisdiction, or perform an internet...
Your child support should be a set number of dollars every month for you child or children. this is to be used for all needs of the child. food, medical, recreation.