*sigh*
Sorry to hear about all that.
If it makes you feel any better.... my brother Matt (who's now 19, and has been living with me for the past year and a half because of his father's illness and death) had HORRIBLE ADHD growing up... passed on from his dad who was almost worse, except for the fact that he was older and not so hyper... and still deals/struggles with it..... but he has turned out to be the most AMAZING, strong, determined kid I know. He pulled all his childhood and middle school bad grades up to AB honor roll in high school, graduated on his own with only my help... and even now that his dad has passed and he's no longer on insurance and cannot even get his meds (for the past 3 or 4 months)..... but he's still rockin it and strong. And going places. Growing up he was so frustrated, and still gets that way, but now he's come to realize what it does and tries his best to keep from losing his cool with it, and letting it dominate his actions and his life.
These kids can do it.... they DO get through it, and quite often it makes them amazing, wonderful people for it. All we can really do is support them and keep them afloat until they know they can do it on their own... and you know what? It's so worth it in the end.