While Ziva and Tony are playing Scrabble, she plays QI + QI and claims it's worth 60+ points. The only way it could be worth that much is if the Q were played on a triple letter tile; however, she played it on a blue tile which is a double letter tile, triple letter tiles are green. The play would have been worth 42 points.
At the beginning of the episode, there are 6 shots fired from the S&W M637: One when the serial killer shoots at Ziva before Ziva knocks the gun from his hand and five when Ziva shoots the serial killer after retrieving the dropped weapon. The S&W M637 is a 5 shot revolver and, as the fight happens so quickly, there was no time for a reload.
At the time the team arrests their military suspect they still haven't matched him to the prints found on the murder weapon. They should have been able to match him very quickly given that they have done so numerous times before via their comprehensive fingerprint database of members of the armed forces. Even quicker considering he was in a small pool of potential suspects.