Failing to deal with an angry 4 year old

I'm steamed.  No, I'm beyond steamed.  I'm so livid at my eldest son that I can't see straight.  And I'm not sure how to deal with it any more other than continue being firm and hoping that he grows out of it when he turns five.

Of late, Teddy has been throwing incredible fits whenever he doesn't get his way.  I won't let him watch or read what he wants?  Not only does he get angry with me, but he hits or kicks me.  It's usually not too hard, but whatever punishment I give only fuels the anger higher.  And I don't feel that hitting should be allowed to go without comment, otherwise I'd just ignore him.

Today was the worst fit ever.  And what makes it worse is that he'd been so good up to this point.  In church, he was a veritable angel, trying to show little brother how you're supposed to behave in church.  Then we went to the grocery store.  And 1/2 way through was when it started.  He wanted to buy yogurt.  We still haven't received my unemployment check so we were surgical striking.  We told him no, we wouldn't be getting yogurt today and he started screaming that we would be and he kicked me.  Rich was ready to bring him out to the van, but he begged enough to have another chance that we granted it.  Then when we were going down the soda aisle, he wanted a bottle of flavored water.  Again, I had to tell him no.  He tried pulling a bottle off the shelf anyway.  So I grabbed his hand and started taking him out to the van.  He yelled and screamed and kicked, begged for another chance and tried the tears.  I wouldn't let it sway me.  At one point, I had to try carrying him but he's too big for me to do so comfortably, particularly if he's fighting me.

Once we got to the van, he tried to run off from me.  I had to pick him up and put him into the van.  Whenever I buckled him into his booster seat, he'd unbuckle himself.  I finally flipped the safety switch on his door and closed it so he wouldn't be able to get out that way.  But if I thought that was going to be the end of it, I was sorely mistaken.  Because the next thing he did was take off his shoes and start throwing them at me.

I was so angry I said some things that I really didn't mean - like I wanted him to go live somewhere else because I just couldn't handle him anymore.  It's something that never should have come out of my mouth because of the anger.  But it's honestly how I was feeling then.  And while me saying it upset Teddy for a little while, within a minute he was back to screaming and demanding.  The only thing that finally got him to shut up was me telling him I was calling Santa to tell him what a bad boy Teddy's been.

Right now, Teddy's in his room, being punished.  He knows that he's in big trouble.  And I'm downstairs, trying to cool off.  And trying to figure out how I let the whole situation get out of control.  Was it when I told him no the first time?  Was it not letting Rich take him out to the van the first time he acted up?  Was it trying to deal with it myself instead of letting Rich deal with it, since Teddy and I seem to be oil and water when we're angry?

I don't know.  And I'm not sure how I'll deal with it next time.  But I do know that I miss my good little boy and I want him back so badly.  I want him to stop hitting and kicking, throwing things and screaming "NEVER!" whenever I ask something of him.  I know there are going to be temper tantrums, but I wish they weren't an every day occurrence.  And what worries me most of all is the fact that I was like this as a kid myself.  I threw temper tantrums, yelled, screamed, threw myself to the floor, whenever I didn't get my way.  And it ruined my relationship with my mom for a long time.  Now I'm worried that the same pattern is happening with me and Teddy.  And I don't know how to stop it.