Sorry you're having such a hard time. Are you sure the ADHD/ODD diagnosis. is correct? Is he on medications? Who diagnosed him? History of any substance abuse or mood disorders in the family? The reason I'm asking is that ADHD/ODD is often a misdiagnosis when it is something else, often a mood disorder. If so, stimulants will not help and can make things worse. I recommend seeing a Child Psychiatrist (forget the Psycologist) for diagnosis. Since Pervasive Developmental Disorder (PDD) is in the family, another genetic diagnosis., you may also want to see a neuropsychologist to rule it out. If you see a neuropsychologist they do intensive testing and can also look for ADHD, but, to be honest, in my layperson's opinion and having had a child misdiagnosed with ADHD/ODD I think it's over-the-top for that. I hope you get another fresh evaluation or two and it works out better for you. Meanwhile, be good to yourself and make sure you take time to relax. You may look into respite until he is stable. Here is a link you may want to have a look at.
http://www.bpchildresearch.org