Bad Questions. Assumed alternatives that do not match actual opinion. For example:

1. What fraction of a population has to be living or travelling in space regularly or simultaneously for the whole population to be called a "Spacefaring Civilization" ?

No answer is correct. A Spacefairing Civilization is not clearly defined, but by most definitions I would agree with the answer is not in percentages. The closest answer is 0% but can't be absolutely 0. If you use travel as the criterion I would think you would have to have regular travel to another planet or to the Moon with at least the appearence of long term continuation, but no number.

For living in space as a criterion, I would say a permanent presence would require about 10,000 people, but that is only a rough number. The answer would be proven by experience as to the number of people needed to sustain a colony without help from Earth. Luxuries could be imported, but necessities should be provided locally or harvested by vessels from the colony.

2. What defines the whole of the spacefaring society?

just ask the question don't corral the answers. The correct answer IMO is simply the group sustaining or initiating the travel or colony. It will most likely be a nation or many nations, but coul be much smaller group with CATS.

3. Based on the percentage and population selected, how many people would be actual spacefarers ?

The percentage of space travellers will always be small, much less than 1% unless we get a space elevator.

Regards,
Mark