My daughter is a little bit younger than your son- almost 17 months, and she has hit a little bit but it has stopped. What I did was say "Ow, that hurts mommy"- without trying to raise my voice- very monotone and without making direct eye contact, and if she tried to do it again, take her hand, and gently rub wherever she was aiming for, and say "Gentle touch, gentle touch" "This is how we touch mommy (or others)" and if she then did the gentle touch, I'd make a big deal of it.
At this age they need to know what is appropriate, and I've found that timeouts and spanking and whatnot- they do not connect it to what they have done- and they do not learn what behavior is good- they just know they get in trouble for something.
As for the tantrums, just make sure he is in a safe place- so he doesn't really hurt himself, and ignore it or try and re-direct it. If you are ignoring- keep it so that you can still see him, but he can't really see you. If you try and re-direct, you might wait fora break in the wailing, and do something ridiculously silly that will completely distract him. Or start playing with one of his favorite noisy toys like you are having a grand ol' time, or ask him a two pointed question- like do you want milk or juice? (That lets him feel like he has a little control- by giving him two acceptable choices, at this age they tend to say no a lot, because then he has power, but that way he can choose either and you are ok with either choice- where I wouldn't suggest ok do you want to go outside or to the zoo? if you had no intention of going to the zoo that day.) My daughter can be having a tantrum and I can ask her something about food- and she will snap right out of it to let me know what she wants.
I hope some of this helps... good luck, I know it is hard. As another poster said- each family has their own ways of handling discipline, and you have to figure out what feels right for you and yours.
Oh yeah.. and the other thing with discipline- a lot of times it is VERY normal to have an effect where the behavior gets worse before it gets better... I haven't seen it as much with distraction and re-directing, but with a lot of the other models of discipline, they have to "test the waters" and you need to stick to your guns, as it were, ride whatever technique you go with for a couple of weeks before you try a different one. It'll be hard, but if you keep changing the game plan- he will not learn what is expected of him.