2) Then why not just bet on the race WITHOUT entering Anakin?
Odds. No one is going to give you high enough stakes on a sure thing. Outside of Anakin racing, Sebulba was a shoe-in to win. By entering the darkest of dark horses, Qui-gon ensured the highest stakes to bet on. Plus, the Force said he would win.
3) True. Nine year olds(especially 9 year old boys) are gung-ho about a lot of things that are potentially dangerous. Generally adults step in and prevent it. I was good at riding a skateboard as a kid, but my mom still wouldn't let me attempt the ramps at the park. Anakin's mother's reaction SHOULD have been "I'm sorry, I feel for you, I really do. And I want to help you, but no way in hell I'm letting my son risk his life to get you ship parts. You can always get new parts some other way, if my son dies I don't get another one."
Not to mention Watto's treatment of Anakin here (and as a whole) is NOT in line with how slaves were generally treated throughout history. Though true, they were often treated as sub-human, slaves were not cheap commodities, at least not good ones. They were generally PROTECTED from harm. Could I beat my slave within an inch of their life for a minor offense? Sure. But now I'm down a field hand, or a doctor, or a chef. They can't do their job if I incapacitate them. Same goes with putting them in harm's way for my own benefit. Even Roman gladiators were slaves that were no longer useful, had proved to be more trouble than their worth, were bought specifically for that purpose(therefore weren't to be put to use in any other capacity) or weren't even technically slaves. They were POW, criminals, Roman deserters and turncoats, and believe it or not volunteers seeking money and glory(but were usually just poor saps with no other options to make a living). Anakin was still quite useful off the track in Watto's shop and as a mechanic, so it's baffling that he would willingly put a slave with a valuable skill in harm's way by forcing him to race.
Being slaves, she knew that there were dick-move ways around her objections. QG could simply go to Watto anyway with the same plan, Watto says the slave will race. Done. When money talks, Watto listens.
Actually, gladiators were slaves with the specific purpose of fighting, and more than likely dying. Pay attention to the scene in Gladiator, with Proximo just before the first Coliseum fight . He's pissed because the "script" dictates that his best guys are going to get slaughtered in a reenactment, but he's not going to make an extra cent for compensation.
4) That one is true, but I'm sure it could have been sold without the demo. Most people "in the know" should have an idea of what the capabilities are by what parts are on it. If I'm looking at a used car with after market mods, I already am familiar with that stuff, so I'll have an idea of what the vehicle's capabilities are or should be.
Which are you more likely to buy: fast or fast enough to win? The only way to show off the pod's true potential was to race it.
5) They demonstrate later on in the film, other ways of doing this....
I just said that was the start.
6) Really the only one I can't argue with, and probably the only reason they went that route in the first place.
The other thing this did was add to the culture of the galaxy. It got away politics and Jedi dogma, and the ever present gun fights and space battles.
Pointless was Greedo shooting first, making Boba sound like Jango, and the insta-party that starts up across the galaxy upon the destruction of the DS2.