My husband and I have 3 kids and are filing for divorce. We will have joint legal custody but he wants physical custody of 1 of our children. How will that work if I file child support for the 2 kids that will live with me? Will he be able to file child support on me since I make more money than he does?

it would probably work like this (and i am just using figures from my head here)
u make 40k
he makes 30k

he pays you 625/mo (25% of income on 2 kids)
you would pay him 666/mo (20% of income on 1 kid)
you would pay him 41/mo. (666-625)
It would be a difference in what the child support would be if you paid him on 1 kid and he paid you on 2. A lot will depend on how much more u make, but I would assume given the %'s in TX, you might be paying him if you make quite a bit more