http://www.amazon.com/Transforming-Difficult-Child-Nurtured-Approach/dp/0967050707I am so sorry for what you are experiencing. My daughter has intense melt-downs (I believe in her case due to PTSD) and it is very difficult to stay calm.
I do just want to say that re: the tomato incident, I get it. Even as an (mostly well-adjusted, pro-social) adult, if I would be tempted to do exactly what your son did. (I wouldn't, but it would be tempting.) I would just choose to avoid any power struggles unless it was a behavior I felt very strongly about.
This book is great:
http://www.amazon.com/Transforming-Difficult-Child-Nurtured-Approach/dp/0967050707