Guesses...

1: 11 million, including 5 mil Jewish citizens (1mil Russian + 2mil each Sephardic and Ashkenazi), 1mil mostly Arab non-Jewish citizens, and 5mil mostly Arab non-citizens (who would become citizens of the Palestinian Authority or Israel when peacetime comes, depending which side of the border they fall on).
2: Those numbers would make it 83%/16% Jew/Arab by citizens, 44%/55% by total population. The Knesset's about 95%/5% or possibly more tilted.
3: 120mi N/S and 20mi E/W, maybe something like New Jersey + Delaware.
4: 10 to 12 million

Agreed with Static that "I don't know" answers would be telling.

A rephrased set of questions I would propose that might be even more telling: Answer questions 1-3 for "Palestine".