A lot of kids find it hard to verbalize how they are feeling so they act out. This is very normal in young boys with dmd. I mean wouldnt u act up if all your friends were up running around and u couldnt. My son was put on meds because of his behavior but once i realized he was only trying to verbalize how angry he was about being different he didnt seem so bad. Just let him know u understand and he will eventually stop with the tantrums and just start brutting like older guys.
My son acts the same way. He gets very angry when he has to change from one activity to another, getting on the bus, cleaning up his toys...leaving the store, etc. I find it very exhausting. It is also affecting his schooling. Another mother here recommends caffeine, so I may try that. Caffeine was one of the original treatments they used before Ritalin was created. She gives her son chocolate covered espresso beans or coffee and says it works well for him.