1) For each farm irregardless of how many farmers of one color are in it only scores 3 points for each city. Whoever has the most farmers scores the 3 points per city.
2) Big meeple is worth 2 small meeples. So if a big red meeple and 1 small yellow meeple were in the same farm, only red would score 3 points per city in that farm.
3) if in a farm the same number of meeples of 2 different colors exist then both players score the same amount. If one player has the pig in that farm then that player scores 1 extra point per city.
agreed!