I just saw this post and it sounds like my DS5. He gets very angry over the smallest (to me) things. I'm glad I'm not alone (however, I do feel for you).

We ended up taking him to a child psychologist because things got so bad that it was just constant worry and yelling and battle of wills. Turns out he has mild oppositional defiant disorder along with being gifted and mild adhd....... But we're trying a new "reward system" that's worked (so far) great for he and his 7yo sister...

Good luck with everything - sounds like you have some great advice here.