My board is 33.5" by 22" (84cm by 56cm) approximately.
The expansion board lies on top of this board when desired/required.
I guess so. I find the board, or rather the areas on the board, a little bit too small to hold one or more units, a power token, and a fortress, especially in the South, when playing with the expansion. But in general I think the map boards by FFG have a nice size.