My daughter has ADHD and is medicated for it. She has always been amazingly active, but she started to have other problems that i could not fix on our own. As someone who carries a veritable pharmacy in my purse its very strange i would have concern medicating my daughter but that how it is. Jaden has always been small. she weighed 24 lbs at her 4 year check up.
I was diagnosed as hyperactive when I was about 7 or 8 and put on ritalin. It stopped my growth so I was taken off of it. It's possible that your daughter's ADHD medication is stunting her growth. There are other options to pharmaceuticals. I know that fish oil rich in omega-3 fatty acids can be good for ADHD. I recommend reading the book "Change Your Brain, Change Your Life" by Dr. Daniel Amen. He discusses various neurological conditions and natural treatments and medications that may be helpful for them. In addition, much of his work is focussed around a type of brain imaging called SPECT which stands for single photon emission computed tomography. This type of imaging measures blood flow in the brain thereby allowing an inference of neural activity. You can learn more about Dr. Amen from his website amenclinics.com
As far as your son goes, it sounds like he is a handful and has figured out your limits and how to get around them. I don't have any suggestions, but it may be of benefit to have someone else around to help you take care of him. Perhaps you have relatives nearby that could help out for a few hours a day or you could hire someone. Just an idea there. I know that it's a difficult situation and I hope that you find something that helps.