Do I have any recourse to get the money back I paid over the years for our girls medical expenses?

My ex husband refuses to pay 1/2 of all not-reimbursed medical expenses for our two daughters. They are now 18 and 21. Over their lifetime he has paid for tricare medical insurance and claims that covers his portion of the 50% medical costs. I too have medical insurance blue cross blue shield but I have paid all out of pocket expenses, co-pays, deductibles and prescriptions. He insists he has no obligation to pay anything past coverage. I have been battling him for medical reimbursement since the first claim. Out of pocket for 21 years was over 7,500.00 for two girls. After contacting his commanding officer in Fort Bragg, South Carolina he was ordered to help and he paid 6x $600.00 total. Then stopped. He claims I misused the insurance coverage. Now he claims he will file bankruptcy if I pursue the issue and stop their stipend child support amount while attending college. He is in the military and it has been a nightmare dealing with him for all these years. All paperwork is notarized with both our signatures agreeing on his paying 1/2 the cost. Original divorce decree States he would pay 74%. I had it amended to help him so it states we equally pay 50%. This is still unacceptable for him.