Dusty getting a Mariachi Band to help El Chupacabra woo Rochelle might be a bit questionable. But when you consider that El Chu, like the other racers, have full teams to support them, odds are Dusty went to El Chus crew and asked them for help.
Another one about Dusty getting El Chupacabra and Rochelle together. He is American, they are Mexican and Canadian respectively. The United States lies between the other two nations, and can be seen as both separating and connecting them.
Dusty being an Acrophobic plane actually makes a bit more sense when you remember that he is, well, a crop duster. The higher you go, the thinner the air gets. You can combat this with a Supercharger to "squeeze" the air to bring it back up to a good air pressure, but that requires some of the engine power to just run the supercharger. Turbochargers can simply use the exhaust gas that is otherwise wasted, but those add complexity and weight. As such, cropdusters, which don't have to fly very high in the first place, will likely just run with normal air pressure. Dusty isn't just scared because of how high up he is, he's scared because he flat out struggles to breath at too high of altitudes.
As for how a Cropduster can hope to hold its own in an Air Race, it should be noted that the model of aircraft Dusty appears to be based on, the AT-802, has an engine that can produce around 1,300hp, roughly 4 times what the majority of modern air racers can produce. With the reduction in drag he received in modifications during the European leg of the race, he would gain a considerable amount of speed, and with the near total overhaul of airframe received near the end of the movie, incorporating several military aircraft parts, he would be EASILY able to keep pace with custom racers that sit at around 300mph at 300hp.
WWII exists in this world. That means there was a car/plane Hitler, and thus a carlocaust...
Cue the mental image of Volkswagen beetles doing the car equivalent of goosestepping.
And of course, for there to be a WWII, there must first be a WWI. Which makes one wonder how (or if) trench warfare works if everyone (on land) is on wheels.
