Child Support issue with child turning 18

I have joint custody. My ex was ordered to pay child support of 189.00 every two weeks for two children seven years ago. Now that my oldest child is about to turn 18 he wants to end the child support. ( I know that he has a legal right to) He also wants the other child's support lowered because i now make more money than he does and he has another child at home with his second wife.
I don't want more than I deserve, but I have had to sacrafice and do without for a long time with the minute amount of support these past seven years. He has not paid a penny more on the children these 7 years. No back to school stuff, no extra help with doctors and dentist bills. He has not supported the children in their extracurricular activities like band and sports. NOr has he helped pay the expenses that go along with these activities. He did not help get the 17 year old a car, nor has he helped with the car insurance and upkeep. Now that we are in senior year of high school the expenses are much greater. College tours and SAT, class ring, graduation stuff, school fees... the list goes on and on. I don't want him to give us more money, just want his share to be fair. We had a custody battle. He wanted custody. I was given primary custody and he was to share in the responsiblitly of the kids. He did for a while. Then when he got remarried and had more children, my children became less important and not a priority. He went from picking them up from school 2 to 3 times a week and every other weekend to only every other weekend. Since he is irresponsible and can't have the children at their events on time, they chose to stay home when they have games or competitions. So now they go to his house even less. Should I take him back to court or should I count my losses and just forget him ever living up to being a dad that really cares about the wellbeing of his children. And giving them the support they deserve. By the way- he has the ablitlity to make more money than he does. He choses not to. He has to drive his 23 year old wife around to her mininal paying job because she never got a drivers license. They treat my younger daughter bad, by making her sleep on the floor and making her baby sit the smaller children. His own family is disowning him. What options do I have?

[Gbyte]

If ur 18 yr old hasn't graduated from high school, he still owes support. Its not unreasonable for him to request a review.

If you make more money than he does, he should have his support lowered.

You can always ask the state to go after him for back child support if he hasn't been paying regularly throughout the years.

As far as his involvement on an emotional level: unfortunately you cannot force a person to be a caring parent. That's his choice.

He can request the child support for the child turning 18 be suspended. She is considered an adult at that age. Unless, of course, there is a stipulation in the child custody order that states he is to pay while the child attends college or until a certain age.