Continuity mistake: When Molly parks her car right at the start of the film, she parks and then the camera cuts to the two guys talking who walks over to Molly. When he walks over she parks her car again. (00:04:00)
Continuity mistake: When Peter and Molly are talking at the start, the amount of bend in Candice's straw changes between angles. (00:05:10)
Continuity mistake: When the bus is falling into the river, some items fall down on to the window with Issac. However the camera cuts and the items have disappeared. (00:13:40)
Continuity mistake: During the bridge collapse scene, when Olivia is crawling on the beam, she is first seen on the part of the beam that is closer to Sam. Almost instantly afterwards, she is on the part of the them that is closer to Molly. The space between the two beams increases significantly between the two shots as well.
Factual error: In Sam's premonition, when Isaac is still in the bus when it is falling down to the water, he is at the front of the bus. In reality the falling force should be pushing him to the back of the bus.
Continuity mistake: In the premonition right near the end, you see the truck hanging over the bridge and that is how the poles and that sheet of metal kill two of the main characters. Yet when they run to the end of the bridge, the truck is not hanging over the edge.
Continuity mistake: During the re-creation of flight 180, the captain announces the lights are being dimmed for takeoff, and the cabin gets dark. In Alex's premonition of the takeoff in the original film, the cabin lights remained on until the explosion. Granted, Alex's actions may have changed some events (such as the teacher celebrating), but if dimming the lights was a takeoff procedure, that shouldn't have changed (either that, or Alex's vision was wrong, which undercuts the premise of the entire franchise).
Continuity mistake: Tony Todd's hairline in this film is almost completely receded compared to the full head of hair he sported in the first film, despite the events of this film being chronologically earlier.
Factual error: Olivia's death starts with her laser eye surgery going wrong. Why did she only have one doctor with her, and then he left her alone? In any sort of surgery, especially ones with expensive machinery she wouldn't have been left on her own, nor would the doctor be working on his own.
Answer: To answer your first question, Bludworth does in fact mention he has "seen this before", but this means he could have seen these events before the film series ever took place. It is possible that this is where he had learned a lot about death's design. This could even hint at another sequel/prequel. To answer your second question, none of the survivors had been alive to tell the tale of what happened to the survivors of the bridge collapse. In the first few movies, it is noted that the protagonist freaks out, thus, startling MANY people. In the 5th film, Sam is only seen freaking out inside the bus. Even if the FBI have the information, they could have finished the investigation completely, due to Sam, Molly, and Nathan surviving (Until the end of the movie, that is).
M0vi3