PR spoiler post should answer the first two, I think.
As for the third, Field Polarity included the Polar Majority/minority players. So if the Field Polarity was neutral, then that means that the majority and minority roles were spread as evenly as possible, pretty much.
Eh...like, if there were 6 players and one each of majority and minority, and the other four players evenly picked dark and light, then the majority would be one polarity and minority would be the other and thus make it neutral.