hearing impaired child with divorced parents and medical in ga?

I have been divorced now from the father of oldest child who just turned 18 for about 13 or 14 years in the state of Georgia. she wears hearing aids and needs other medical procedures done. she moved in with me and i am a stay at home mom of another young child nearly 9 years old. current husband is self employed and carries no medical insurance. my 18 year old needs her wisdom teeth pulled out, as well as some other things with her eyes, and her ears. she is still a student in high school as she has been held back several times and has yet to get her permit for driving nor does she have means of income of her own.

in the custody papers, we have joint legal custody and he is responsible for her medical and education. he has stated that he will not pay or help in any way the cost of the expenses in the needs of our child because she no longer lives with him and she is now 18 years old. he has also been giving me a difficult time about cooperation on the medical policy with information and what the policy will and wont cover and since i am not on the policy because of the divorce and remarriage i cant call the policy and get information myself.

i am way limited on money so please help so i can fight him to get some help for our daughter whom he seems to be abandoning even though she is 18 she has medical needs for the rest of her life