The ones who survive, which has little to do with their own choices, such as remain to them. That assertion is utter nonsense. By that light, there is no problem with false imprisonment, because they get to go home when their sentence is served. Theft is not justifiable by citing an intention to return the stolen property, if it is still intact, once you decide you are done with it! Assault is not acceptable because you heal afterwards, and slavery is not acceptable just because it's temporary. For thousands of Americans and millions of Europeans and Asians, conscription has lasted the entire remainder of their lives.
I don't know, neither do you, and it has nothing to do with anything else.

Because they use the Force for knowledge. They have access to special insights and guidance, that no one else does, and no one else has military experience on the scale required to lead a brand new army, in numbers of individuals committed to the Republic. Also, they didn't really do what generals actually do. The ranks seem to be a courtesy for the sake of the soldiers, who need such things to understand peoples' place in the system. What they actually do is guide the fighting men, and protect them, by taking out major threats.

Star Wars is actually fantasy. Just because it's in space does not make it science fiction. There is nothing about science in it.