1. b, 1%. Fairly arbitrary, but I think if you've got too few actual spagegoers, then it's more of a spacefaring club than a civilization. Kind of--I suppose--like what we have now. But even just 1% of several hundred million people is a large number of astro-citizens.

2. f. But I wonder if it'll fall out along more general lines. Given the nature of politics and economics, participation amongst trade-block members might be more likely, but if a country has the technical chops and can be worked with, then maybe they can be part of the group despite political differences (*cough* China *cough*).

3. i, 10 million. Seems somehow more plausible when expressed as "1%." Are we ever going to have a million people in space at once? Probably only if they get knocked off the planet when the asteroid hits...