It's tough to say because the Daytona 500 is the Nascar Super Bowl and more fans like Nascar than Indycar, but the Indy 500 racetrack has more seats than in Daytona. So I think more people go to the Indy 500 just because the track has more seats and the Indy 500 is the most important race in motor sports.
Yes it is. Heck, no! * The amount of fans for NASCAR are about the same for pro football. Not exactly.. Nascar has more fans than football, seeing how the people in other countries who are football fans are actually "soccer fans"
Nascar has about 75 million fans.
The Indy 500
None, Jr races NASCAR not Indy.
A lot less than a Nascar
Definitely yes, I don't have the figures but outside of the US Nascar is not well known, whereas Soccer/football is extremely well known and watched.
The purpose of car sponsorships in NASCAR is to gain more attraction and fans. In addition, the purpose of car sponsorships in NASCAR is to gain more support for race car sports.
NASCAR fans will watch football. Though races may interfere with football because of the time of the race and game, fans can watch both sports. It's possible to like more than one sport.