divorced in bexar county tx 3 yrs ago, i need to find out what is necessary to modify support. we have 18 yr old son in college and I am the only one paying for education and housing. Is it possible to modify decree to make father continue support or pay 1/2 of education expenses. He stopped paying for him and has had several increases in pay at work. IS SUPPORT BASED ON WHAT HE ACTUALLY MAKES OR IS THERE A MAXIMUM?