Time-Out. Ouch!

I have begun to more seriously address a problem we've been dealing with for at least a year.
Throwing.
JD throws cars, crayons, stuffed animals, plastic animals, books, food, cups, blocks, puzzle pieces, hockey sticks, train tracks, trains, and, of course, balls. Fortunately, he has yet to throw something breakable like a plate or glass. I've told him that he's allowed to throw balls (trying to allow for a positive - something he's allowed to do.) He seems to know that limit. He also clears papers and the like off of tables and I consider that throwing, too.
The biggest problem is that he throws things like cars and blocks at people. It was cute for a bit, then annoying, now infuriating. I've let him know about it every time he throws something since he first started. Now that he's got some vocabulary, he'll throw something, look at me, and say, "No throw!" Sometimes I want to laugh and other times my head wants to explode.
Tonight, he threw a bus at me. A toy bus about 6 inches long and metal. It's heavy. It hit me in the wrist. I had to count to 10 a couple of times before I could be rational with JD. He's only 22 months, I had to tell myself. Then I picked him up and took him for a "time-out."
You've all heard of or used times-out. Some people believe in them, others don't. I've discovered several things about the time-out. First, they are as much for the adult as they are for the child. Second, they have to be meaningful. Third, they have to be consistent. Finally, sometimes they have to hurt.
I've discovered that I have a short temper with JD when it comes to things I've told him over and over. Putting him in a time-out allows me to compose myself. I'm convinced that he now knows when he's doing something wrong but can't control his impulses. I have to be able to control mine. A minute or two (or longer, as I'll get to) will help me relax and be able to get back to productive exercises with him.
Putting JD in a time-out doesn't help if he doesn't know why he's going there. When he throws something, I pick him and the object up, bring him to his time-out area, and show him the object. No throw cars. Cars hurt. No throw cars. Time-out.
If I don't do it every time, then he probably won't know when he's misbehaving. Every time he throws something he's not supposed to, it's a time-out. No questions asked.
You may have read the hurt thing and thought physical. No. Here's what I learned tonight. I had been putting him at a chair at the dining room table, the emptiest room in the house. There's nothing to do, nothing to distract. After a few moments, he would get up. No matter how many times I put him back, he knew he could get up. He would smile and sing to me and laugh. He wasn't getting the point; it was a new game.
Tonight I buckled him into his high chair without the tray in the dining room. Then I walked out. That took the fun away. He had to sit there and he knew it. It didn't take long for him to start crying. And I let him cry. For a couple of minutes. Then I took the steps described above. He appeared much sorrier than he had at any other time. It hurt him to be locked up like that. He knew there was a reason he was there.
Many of you may strongly disagree with what I'm doing. I feel like it's a safety issue. Those are the times when I enforce strong discipline - when it's a matter of safety for him or for others. Just as importantly, he must respect my word like the word of G-d. If that means I have to hurt his feelings from time to time, so be it. It's better than someone getting hit in the face with a random object. And I believe he respects the boundaries that are set for him.
These are the terrible twos. He's testing his boundaries and crossing them whenever possible. Boundaries are like walls; sometimes I'll help him climb back over, other times I'll throw him over. One way or another, he'll know when he crossed.