As to the Endor moon being visible outside the window: The throne room is located on the top of a tower at the Death Star's north pole. The main window would face deep space and the space battle - not Endor. I think that one or both side windows could face Endor, though.
Good call.. Still the room is rotating so we can see endor and the battle as the time passes.. Plus gets more visually interesting
Not sure of the surface, too lazy to calculate..
Edit: thanks 005 :D
-Angel