You are in their lives!
Child support is calculated using a formula (states use different formulas).
What did you do before the divorce? I find it hard to believe that suddenly after the divorce you would find yourself limited to "dead end" jobs.
Oh, and FYI? You aren't paying "her", you are reimbursing her for what she has to pay to care and provide for the children! She pays out of pocket for EVERYTHING (mortgage/rent, utilities, food, etc.). The least you can do is reimburse her for a portion of the costs.
This is all about the money. This is NOT about the children.
If you cared what was in the best interest of the children, you would quit whining, put on your big boy underoos and enjoy the time you have your children.