Since it's never referenced that we saw the entire 5 year mission, it doesn't count.
I never thought being a redshirt was an automatic death sentence (beyond as a source of amusement), but realistically, being in security is all about being able and willing to take the risks to defend your crewmates.
Yes. But I mention the myth because it's a popular one with the general audience who often aren't knowledgeable about Trek. My thought was their accepted myth doesn't really hold up based on the episodes that they could have seen. Whole stretches of episodes go by without anyone dying.