Question: Why does Owen visit Nicky at the hotel where he stays with Jess? And why does Nicky get tensed as though they are strangers?
Answer: Because Owen is really Nicky's father, Owen. He was making sure he stayed focused on the con job, not his girlfriend. That's why Nicky was tense, like a stage play you're supposed to remain in character not matter the situation.
Question: What was the red sports car Will Smith was driving - the one that was smashed? Perhaps a Ferrari California?
Answer: It was a 2013 Peugeot RCZ.
Question: Would it really be possible to trick someone's brain, the way they did with the number 55?
Answer: Absolutely. There are many people (especially people who work on high commissions and con men) who are well practiced in subtle cues with body language. The elaborate process they went through in the movie greatly increased the chances he would make such a pick, but there was no guarantee. However, it was constructed with personal knowledge of the target. Even more strange was the fact that a string of some of his reasonable bets went bad (the missed extra point, the pick of the card, etc). Had they all not gone bad, it would have disrupted his faked desperation to the multi-million dollar bet.
Answer: She recognized Farhad wearing the Jersey number.