I have a very strong opinion about your last question:
Please hold him and help him calm down and THEN make him apologize. There's an old saying, "Never argue with a drunk," and it applies here too. Your son is not in a rational state DURING the tantrum and intense frustration. It is AFTER you help him calm down that an apology can come from a sincere place. I think it's extremely encouraging that he asks for comfort in the first place!!
Another resource you can check out is Love and Logic Parenting materials. You can get them cheap through half.com but can find out a lot about their philosophy at their website. I think their website is loveandlogic.com
Good Luck- I have a three and a half year old tantrum boy too so i share your pain!!!!!!
