1) She wants him medicated because she doesn't want to be bothered with him. It's as simple and crappy as that. Watch for her to attempt to doctor hop until she finds one that will medicate him and then you can consider the possibility of going to court over it and getting an independant evaluation ordered. That will be an uphill battle. Read everything you can about ADD/ADHD if she pushes this.
2) He shouldn't be running around with a bunch of other kids at age 8 so give her that if that's what happened.
3) The overall problem is a lack of consistency, lack of guidance and proper discipline and further, a lack of real give-a-sh*t on your ex's part because it interferes with her and Prince Charming.
4) You're either going to have to get on the same page as her on this matter or draw the line, pick your balls back up and fight her. She's a talker and she thinks she is full of wisdom. READ so you can put her in her place.