Child support is calculated based on income. People paying it feel it is too much. People receiving it feel it is never enough. Parents paying daycare understand child support usually doesn't even cover those costs let alone clothes, shoes, haircuts, birthday parties, etc..
It is fairly common knowledge that Texas calculates child support based on the non-possessory parent's net income: 20% for 1child, 25% for 2 children, etc. Their website provides information on how to calculate child support for your particular situation.
Texas does not care how much the other parent makes, whether they are being supported by a boyfriend or others. It is all about income. If the the non-possessory parent is unemployed, works part-time or is a student, child support is calculated at minimum wage.
If parents are considering split custody (50/50), each parent's income is taken into consideration. A 50/50 split requires good communication as well as living close enough so that getting the children to and from school and activities is not a burden on anyone.
Medical costs are usually split 50/50 between the parents. Make sure you submit the bills to the other parent promptly. Contributing to the cost of providing health insurance is also seen as additional child support (but the cost must be the amount just to cover the children). Parents are ordered to cover those costs regardless of who carries the insurance.
Child support, possession, income, health insurance, out of pocket medical expenses are issues that you should become very familiar with. The Attorney General claims they review child support cases every three years. You can hire a private attorney to review your case and determine whether filing a modification or enforcement action is appropriate.