Your creature should teleport to you if you get too far ahead. You can always unsummon / resummon it when you notice opponents ahead, or before entering caves, etc.
The 3 levers in the bunker switched off the barrier blocking access to the rest of the fjords as well as the anti-dragon shields around the bunker (you can fly back now directly, and transform over that ledge, if you wish to visit the merchants there, without having to teleport over). There are anti-dragon shields around High Hall and the harbour, if you've been that far, but no way to disable them.
A second barrier exists in the channel south of the harbour, but can be lowered by destroying the defenses there (specifically, 4 ballistas surrounded by a blue lightning kind of effect). You can wait until you have leveled and become more familiar with the dragon form before doing that, though.
