Just letting you know that I'm here in solidarity with you. My daughter is 6 and is having HUGE emotional swings, from cry-fests to jealousy of other kids, to absolutely raging tantrums. We just contacted a child therapy place to get an appointment so she can have an outlet for some of these emotions. We don't know how to deal with it anymore at home. It's to the point where we do have to go old-school parent and shout as loud as we can during the tantrums to scare her into stopping the behavior. Nothing else works.
Do you have anything that you share with him? My daughter loves father/daughter time - we go for bike rides alone, do puzzles, play board games, etc. If you have a shared interest (even if it's video games or movie nights), maybe that will help take his mind off of the negativity and reinforce the positive family influence.
I also agree with the physical outlet - sports, martial arts. Wrestling helped me when I was a teenager, and my nephew (who is mildly autistic) thrives in full-contact football and martial arts.