I am going to start this off by saying that I could have interpreted the worksheet wrong, but from what I can tell.
1)No you cannot count child support from a previous relationship as income. The order that is between the two of them is regarding the support of their child. And if you think about it, the amount that you pay should not be reduced by what she receives from that relationship because he is under no obligation to support your child.
2)The worksheet states "Children's portion of health insurance premium." To me, this sounds as if you would take the total additional premium of what it takes to add children to the policy and divide it by the number of children. So if its 90 dollars to add them, and you have three kids, then it would be 30 dollars for each of them.
Here is a link to the worksheet.
http://www.tennessee.gov/humanservic...ines-downloads
There will be other posters who stop by who will correct me if I am wrong, but from what I have read, this is how I interpreted it.