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.
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