The Fertilizer Nitrogen-Phosporus-Potassium are shortened as NPK, not as NPP as shown in the movie. The letters NPK are the symbols for Nitrogen-Phosphorus-Potassium in the periodic table. In this K stands for Kalium, which was its Latin name.
Kirby uses a statistical correlation of the time it takes Arrow to get to crime scenes to triangulate back to his hideout. This would only work if it were established when Arrow found out about each of the crimes; he has been shown several times to be there prior to the police, so his source of information, and therefore his actual journey times, can't be known by someone else.
Felicity says NPP is an acronym, which is a common misconception. An acronym is initials that spell a word, like SCUBA. Letters used to stand for something that do not spell a word are known as initialisms, such as CIA, BBQ, etc.