Am I right in saying you don't feel confident that your child really needs those medications? Your post sounded like you were against the decision at first but now think they might be having a positive result - is that right?
It seems to me that the first important thing to remember is that a doctor put your son on those medications, not your ex-wife. I mean I guess she took your son to the doctor because she had some concerns about him (legitimately or otherwise) but ultimately, it was the doctor that decided the best thing for the child would be to prescribe medication. Otherwise surely he/she wouldn't have done it?
If I were in your shoes and I really wasn't sure of whether my child needed the medication or not, I would be raising the issue with the doctor concerned. Afterall, they are legally responsible for their decisions. And if after that conversation I felt the doctor was wrong (or I was still not convinced) then I would get a second opinion from another doctor. And if I didn't have custody of my son or if my ex-partner refused to allow me to do this for whatever reason then I would be getting advice from my lawyer, with the aim of requesting from the court that a second medical opinion was sought (on whatever grounds you felt the first decision was wrong).
As far as the astrology goes, and wanting to help your son, it would seem to me that the best thing you could do for your son would be to arm yourself with as much information about the medical condition as possible. Also, I'm sure there are hundreds of support groups out there for parents of children with this condition and they will have well researched advice about alternative methods of treating the condition in addition to, or completely separate from, drugs.
My point is that, in my opinion, the insights gained from analyzing an astrological chart are always ultimately limited by the fact that the chart only ever shows the potential for certain things to become manifest, there is never any guarantee that those things will actually happen. So whilst, you are arming yourself with information about his personality derived from his horoscope, there has to always be a fundamental requirement that you do not neglect to pay attention to what is real - what you do actually KNOW has become a reality about this child. And the only way you will ever actually reach a strong strategic position - as far as the doctors, lawyers, and your ex-wife are concerned - is if you relate this insight to recognized medical knowledge about the condition.
I wish you good luck with everything.
Warmest regards, Nicola