I checked Amber´s Peak with my early sketches. As you assume, the observatory doesn't have a map, and the ”E” shouldn't be on the map at all. The picture on page 85 should only have a ”D” in it (The observatory had it's own number in my draft). The observatory is reached on a stone bridge from where the pyrotaur stables are (10). No separate connection to the castle. See the overview. The stairs from the observatory lead down to the plains. In my draft however, there were no plains, but a lake or the sea behind the castle and the stairs led down to a harbour. From here monsters were shipped to be released further down the shore, not to be connected with the castle.
Concerning the compass directions: up on the page corresponds to north-north-west, that is: north is tilted somewhat 30° counter clockwise. Why is this? Well, it wasn't easy to try to fit the map to the picture on the box