1. Science and Technology.
Everything else will experience a cascade-effect of benefit.
2. Large military fleet.
For one thing, it provides excellent standing defence. For another, it also provides excellent in-space infrastructure, which will be crucial to an interstellar-capable polity, which I assume is what we're discussing.
It also provides a basis for a merchant marine, commercial transit, and rapid colonization prep.
3. Infrastructure is key. Quality of life, is not.
That's not to say that quality of life is unimportant, but that it would be supremely difficult to give everyone max quality of life, and would probably also promote a highly lethargic populace that can't get anything done.
OTOH, give them something to work for, to do, and you get a high-productivity, happy populace.
4. Both. As Ryat mentioned, balance here is essential.
5. Yes.
There are some things that the public just should not know. Whether due to suppressing information to prevent general panic, or to prevent outbreak of war, that's the difference.
6. Military power is important, but not all-powerful.
I'd actually have a much larger merchant marine (armed merchant vessels/warships with high capacity cargo handling), and a relatively small purely militant navy. This provides excellent armed merchant convoy capability (crucial in wartime), and also increases prosperity in peacetime (high trade traffic).
7. No.
As I see it, generalist democracy is a failure. Even a mixed-democracy is exceedingly difficult to implement. OTOH, I'd go with a combination meritocratic/technocratic system. This is, incidentally, an effect of emphasizing technology and science advancement.