ADHD & ASD

I'm new to the group and I'm sure this question has been asked   many times. My son was recently diagnosed with ADHD and shows signs of ASD and awaiting assessment (which i have been told has a current waiting list of a year and half). I am already convinced he will be diagnosed with ASD already and have been managing it from a young age. My main issue now that he is 11 is that I'm struggling with his behaviour, he is constantly on meltdown and I find myself constantly having to shout and ask him to do things, I do try to avoid the shouting match by sending him to his room but he refuses to go and just continues for hours at a time. I removed his Xbox as felt that he was becoming addicted and feel that his friends are all online (although none of this friends he plays with in school) I did tell him that when he learns how to talk and be respectful etc he can have it back. In school he is the class joker and hates to do any school work although seems to be managing alright, it really concerns him what people think and does not have these verbal meltdowns at school and will just cry if there is a situation at school. The same at his football lessons if a kid says something bad to him, rather than respond he will get upset and cry and embarrass himself. He constantly tells us and his grandparents to shut up and than denies it even though we all witness it, the same if he does something that he shouldn't and we witness it, he will deny it. It sounds petty I know but it's every day and don't know what else to try. Any suggestions?