Kudos to you for being proactive while your son is still young. You're describing many of the behaviors my son demonstrated. Unfortunately, we waited until our son was 14 to get him evaluated because he wasn't a huge behavior problem, just had focus issues and we perceived him as lazy, impulsive, forgetful, dishonest and unmotivated. As you can guess, he has ADD (no H) and now that he's being treated, life is way better. I wish we'd done something years earlier.
One thought about the "headache" when there are distractions. If he does have ADHD, the word headache may be what he uses to describe brain overload since he's not able to tune out everything that's going on around him.
Feel free to PM me if you want to talk more. Good luck!