Jor-El was the only person who thought Krypton was going to explode. He might have been Krypton's most respected scientist but Einstein was our most respected scientist and he didn't believe in quantum mechanics. The Kryptonian ruling council was simply interpreting the evidence differently than Jor-El.

The very history of Krypton can help earth immensely. Krypton has much history than earth. By learning about Krypton's history, it would prevent, or at least reduce the chances of humans making the same mistakes as the Kryptonians, mistakes we haven't made already.

About Book, choosing the lesser of two evils is easy compared to living with it for the rest of your life. I’m sure you’ve heard the question “would you kill ten people to save the lives of a hundred” or something similar but the more difficult question is “can you live with yourself after that?” Even if that was the only choice, that the only way in the entire universe to save those hundred lives was to kill those ten people, you will doubt yourself after committing such an act. You will doubt everything you have ever believed and will ever believe. You will doubt your every action. In every step you take there will be fear and suspicion and disgust. You’ll never really live again, you just endure. That’s before you start thinking about confronting the families of those you’ve killed. Looking into the eyes of their children, telling them that you killed their parents, hoping that they will understand. It is an unimaginable torture, your reward for doing the right thing.

I think the movie does a magnificent job in dealing with Book's past in that it both answers it and leaves it open. The movie does seem to suggest a parallel between Book and the Operative, especially since they both talk about "faith."

But... the movie never says anything explicit about Book's past. If we (hopefully) get more from the 'verse, Book's past could turn out to be very different from what the movie suggests, without contradicting a thing because nothing was definitively said. And for those who doubt whether a sequel would delve into Book's past, both Joss and Chris Buchanan have suggested that they can find a way without overturning the BDM.

So, in short, you may well be right GiantEvilHead. The movie doesn't definitively answer it one way or another, which is the smart way to play it. To find out the answer for certain, everyone should buy the DVDs and convert more folks so we can get that sequel/continuation!