At the risk of sounding unhelpful, this is really not an apologetics question. This is a medical and psychological question, and should be discussed with your son's doctor and with a counselor who specializes in helping children with ADHD. You may want to call the Pastoral Solutions Insitute
, a Catholic counseling apostolate, for counseling or for a referral to a specialist in your area.
In the meantime, since it sounds like your current disciplinary methods are not working and you are in need of immediate short-term solutions while making arrangements for further counseling, you might want to see if there is a Parents Anonymous
support group in your area.