Visible crew/equipment: When Jason Statham is falling from the helicopter, you can see a pole that's either a camera pole, or some other type of equipment used for the scene. It definitely isn't supposed to be there.
Continuity mistake: When the man has a hole burned through his throat, in one shot he has one hand on his stomach and the other by his side, but in the very next shot both hands are on his throat.
Answer: It's never fully explained in the movie, but it seems more likely that Rayna simply had a lot of enemies and people we're trying to kill her for various motives, but not to steal the nuke. For example, the guy who tried to poison her seems to do it out of spite for Rayna. The steward on the plane seems more intent on kidnapping Rayna to get what she's selling (although the pilot before dying says "Stan and I already sold it...", so he may not be after the bomb). Karen Walker, who was a double agent who sold Rayna the CIA names, is more likely trying to kill Susan to avoid being found out and not Rayna. Although if Karen was trying to kill Rayna, she may have already discovered the bomb's location, through various means.
Bishop73
Right, when in the basement, to make Susan believe him, Fine asks her "Did (or didn't) Karen try to kill you?" And Susan realises he had sniped Karen and her driver to save her from being killed by Karen.