After a race, you get 200 or 300 points depending on how well you're ahead.

How many points is needed to fully unlock everything?

Edit: Or how many points for each dvd?

You mean unlock every part? As far as I know parts are unlocked after beating specific number of races, although I may be wrong.

Reputation doesn't seem to affect anything as you unlock DVDs depending your car's star rating and you unlock parts after a certain amount of races.

Doesn't it affect the sponsors you unlock? I remember reading up something like that a few months ago (but obviously source credibility is always a question)

Not that I know of.

Reputation Points probably just affect how many sponsor choices you get to choose from, when you are given the option to choose a sponsor.

You can get 100 points if you win a race by a small margin, 200 points if you win a race by a medium margin, or 300 points if you win a race by a large margin.

You can get 0 points if you only just barely win by a nose, like if a race ends in a photo-finish.

You get money if you win a race, even if you don't get any reputation points.

The more reputation points that you earn on average, the more sponsor choices you get to choose from.

If you can't complete all 223 races for whatever reason, in the PS2 version, it's because depending on which sponsors you choose on the PS2 version, you'll either end up with 220 races, 221 races, or 222 races, but never all 223 races, due to 1 race being missing from console editions, and being PC exclusive.

That, or you could be missing an SUV race, or a hidden race, or a race that changes locations if you quit the race after losing, and it's one of the ones that doesn't show up in the Garage races as being Not Completed, if you haven't won that race.

You may have to redo all the Garage races, even the ones that say Completed, and make sure to restart them before racing, and to even redo them in an SUV as well, until you find the one that although it already said Completed, it gives you reputation points and money.