The key for the mine can be found in the quarry tower (both it and the top of the wall are still above the poison gas), which is a little north west of the mine.
All of the anti-dragon shields can be shut down. Since you have the generator by the mine disabled, the next is a little south east of Lovis' tower; once you can get in that section...
you need to take a teleporter to another area and find another lever. After that there is a generator/lever to the west by Maxos temple. The lever for the last anti-dragon shield is a little west of the shield.
