This sounds hellish. I'm so sorry.
One of my children - also three - has temper tantrums when she is over tired. So with her I just have to try and organise the day, pace it, so that she gets as much rest time as possible. ITt's a bit easier for me as I don't have to go to work and we don't need to get to nursery on time - so I don't have the same time pressure (when I do it is INFURIATING and exacerbates everything). She still has them though - her new trick is to shout MUMMY YOU'RE HURTING ME (when I, say, try and restrain her to stop her from running into the road). That definitely gets the front doors opening. Her last tantrum - on the street at night - I had to stay very calm and in control and talk her down.
THe other one recently started tantrumming - i think copying her twin sister. THe most epic one last week involved her stripping off to her tights at night in the middle of the pavement in the rain and screaming for half an hour. I even had a 'helpful' passer by shout GET SOME CLOTHES ON THAT CHILD. I finally did what I never do - I said I'd punish her if she continued by not taking her to the puppet show the following day - and then followed it through. This was a week ago. She has been angelic ever since. I tried this again on her sister tonight (she was balking from going to bed). I just calmly said, if you don't stop I won't be able to take you to so and sos party next week. SO please do stop. And let me tuck you in. Amazingly, she stopped.
My best friend said I had to remember that I was in control, that I'm the grown up, and that I shouldn't loose my temper (It's true that this is never helpful). But yours sounds like a long standing problem, and really horrible. Are there any parenting style courses in your area you could go on - just talking about it with someone else might help give you distance.
Anyway, it will pass... And int he meantime, I sympathise.
(PS my childrens tantrums have definitely decreased over the course of the year - they are nearing four now. Also, does he do it at nursery? If not, it's more about your relationship with him than something inherent in him (and you will know then that he can control it under different circumstances, which might be helpful. Infuriating, but helpful).