He clearly displays emotional disturbance beyond the ADHD. Such behavior can be indicative of Oppositonal Defiant Disorder, Conduct Disorder or even Mood Disorder. I have two suggestions. The first is to arrange a reassessment of his medication. The current regimen is not sufficient to address the behavioral disturbance. The second suggestion is to pave the way for his referral to a school that specializes in teaching students who display behavior disorders. He cannot be taught successfully within the regular educational program. If he has never been evaluated under provisons of the special education laws in your jurisdiction, it's important to arrange that evaluation.
You get help for yourself as well.......dont leave yourself out...the more you are filled up the more you can give out....and I am sure the stress is great in your home....get help even for the other child...but get help for all of you! No one should suffer alone without help! Not the mom or the children. There are people who are WILLING to help you and your family. Keep reaching out until you fnd what you are needing. Dont take second best. Get the Best!