for one kid, you get 20% of his NET income. not GROSS income. NET income is after he's paid all his taxes and insurance for you daughter, but before stuff like 401k.
edited to add: Texas child support is NOT dependent on how much the two parents have the child. It's just a straight 20%, so even though you are doing 99.9% of the work and have her 99.9% of the time, it has no bearing on how much child support you get.
You get ZERO credit for day care, so it doesn't matter if you spend $100/mo or $1000/mo in day care, you are 100% responsible for it. He won't be forced to pay any of it.
SO.... you need to add up what he's paying you and compare that to what you would be getting under traditional Child Support guidelines. If you are getting more, I would probably not rock the boat and slowly save up for a car yourself, buy it, and then give his back. If you are getting LESS than the tradition guideline, then hire an attorney.
pretty simple math here in Texas when it comes to child support! :)