Elise is said to have an MBA from Princeton. Princeton does have a business school at the graduate or undergraduate level. The closest would be a Masters in Economics but it's not a professional degree.
Rob ask Elyse if her bowling ball is a custom Storm. Elyse say it is but ask how did he know because it is unmarked however you can clearly see in multiple shots while they bowl and during their conversation that the ball is clearly marked as a Storm.
Sam is a security guard who works at elevator entrance in huge office building in which most of the movie takes place. He clearly works 24/7. Not only it was never show that anybody else work on his place, but it was especially absurd at Halloween - he was working in the morning, afternoon, evening, night, and then the very next morning, and he was very important for the plot. This happened again in a few days later.