When Jimmy is trying to break up Ms. Fowl and Thomas Edison, he hides in the tree and when he falls the invention lands next to him. When Thomas picks it up it right next to Thomas and they are far away from Jimmy.
Edison dismissively refers to Henry Ford as "such a knucklehead". Historically, Edison had great respect for Ford's work, and the two were close friends.
While Edison was and still is well known for his experimentation with and promotion of direct current, he didn't invent it. It was first developed in the early 19th Century and would gradually be further developed over time by a succession of experimenters and engineers. Furthermore, Edison was largely against alternating current, which was an important development in electric power.
In reality, Thomas Edison had little to do with the invention of the radio, since Marconi based it on a device invented by Heinrich Hertz to prove the existence of radio waves. Moreover, the key component of Hertz's apparatus was an induction coil, which was invented in 1836 - over a decade before Thomas Edison was even born.
One of the central conceits - that Edison disappearing from the past would outright prevent many important inventions and advances - is deeply flawed. While Edison was an important figure in the proliferation of electric power and did invent (or at least improve upon) many things we take for granted, it's very doubtful that him somehow being removed from history would prevent the development and proliferation of modern electric power, or the invention of most electrical devices and machines.
When Jimmy disputes Cindy's report, he doesn't mention one of the most glaring problems: she claims that Guglielmo Marconi invented the radio in 1870, when Marconi wasn't even born until 1874.