There can be a fine line between ADD/ADHD and not being challenged enough too. Often it's a bit of both, and doing more to challenge them can be as effective as any other treatment for ADHD such as medication.

Diet is very much linked also. These kids generally react to preservatives and sugar, so the failsafe diet is well worth trying. Also, fish oil supplemements can be helpful for concentration also.
this is a very good point MR
we had him on a multi vitamin for a while and it seemed to calm him a bit we had less outbursts, and he was more reasonable.
that the other thing when he is in his mood there is no reasoning with him or talking to him sensibly he just gets tunnle vision and doesnt listen.

family counselling may be the way to go. all go in sit down and talk in a non threatening environment.