I have four kids and one of my sons seems to be very similar to yours. He was over the top even as a baby and over time I think I have discovered a few ways to teach him to take it down a notch.
First, with him, I learned pretty early on that he is a very scheduled, routined, black and white person. Basically if we typically eat lunch at 11:15, we cannot vary or he will start getting VERY worked up and emotional about everything. If he and his brother are playing and part of the game takes a turn that he did not have laid out in his mind, he flips out. If his shoe laces are not even he will stop until we can fix it. All silly little things but very important to him. We have learned that gray areas will trigger his emotions. So you are right in paying attention to your son's triggers. You cannot protect him from all of them as he needs to learn to work with all situations in life but then again, you can't be cruel and disrespect his needs either. There is a middle-ground that you can get to as you work with him.
Second, I am very stern with time out. Each of our kids have their own spot they are sent to when they are not behaving properly. I know you said you have tried time out before, but once I read your result, I was wondering if maybe the time out was a bit loose. We do not call it "time out" at our house, we have a special spot for each kid, e.g. my emotional guys spot is the living room couch so we just call it the couch. When our kids act inappropriately we physically take them to their spot, give a brief explanation as to why they are there and leave. If they get up, we go back and put them in the spot again and leave, no words. When my son was younger, he could sit and carry on out there forEVER! It was very hard to bear, but the whole family knew that he was to be there undisturbed until he was done. Once he was done, I would go in and talk to him about why he was there, he would say sorry, we hug, it's over. This technique, if consistent, and you don't spend time trying to talk him out of a tantrum, works amazing. The key is to do the same thing every time no matter what. I have seen my friends try to reason with their kids or just ignore them and it just doesn't teach them to correct the behavior. You tell them, sit them in time out, get them when they have calmed down. I can assure you, my son has major saying power and throw a fit for the longest time but this technique has worked and he now has learned to calm down nearly right away and ask for me to come get him, we do apologies and we are done. He very rarely throws a tantrum ever anymore (he just turned 5, his worse ages were end of three through middle of 4).
I have not found that ignoring works that well. Every time one of my kids acts in a way that I do not find acceptable, I instantly correct it and if need be send them to their spot. I do not give the opportunity to negotiate, or go into a lot of detail, it just doesn't work. The best is, get in, get out, act upon what needs to be corrected swiftly and CONSISTENTLY.
I hope this helps, it sure worked with us.
Good luck.