Unless you offer to take care of the ghost yourself, you can not get the key to Gobie's house. There is not a huge difference in rewards how you complete that quest, though (telling Gobie you will kill the ghost is a little better), and not really that much in the house (a couple of chests with random loot).
The anti-dragon shields around High Hall and the harbour can not be turned off.
Kali's flying fortress is in Rivertown Gorge (it is the same location, but gets 2 entrance markers on the map once you have been there).