Needleman's storage is low and directly south east of the tower. From the air you should be able to see the blue glow around the door and a portal on the same ledge.
You can not get back into Lovis' tower after taking over the battle tower.
Here is a
map showing the generators and from the walkthrough:
Broken Valley [FLBVF]
-------------
Location: Broken Valley
-To disable the anti-dragon zone around the mine, you'll need to find a
generator just west of the mine and flip a nearby lever in human form.
-Another lever can be found just southeast of Lord Lovis' tower.
-The next zone to disable requires you to land in the area only accessible
after flipping the prior lever (west of Lord Lovis' tower, just north of the
still active zone). Find and use a teleporter after you land, then locate and
flip the lever at the top of the new area to disable all but one remaining
anti-dragon zone.
-Next, disable the barrier by landing on a platform on the west side of Maxos'
temple and flipping the lever there. Geshniz's Headquarters can be accessed
via the teleporter on this platform.
-The last anti-dragon zone can be disabled by flipping a lever not too far
west of the zone itself (like the others, it's found inside of a thick-walled
fort easily visible on the map).
-Doctor Needleman is sitting on top of Lovis' Tower. You can mind read him to
gain his storage password. Find his storage south of the tower, right next to
the portal to Stone's Flying Fortress. The key to the door inside is hidden
beneath a few barrels to the right of the door. Unfortunately, the loot you
find isn't really worth the mind reading cost.
-You find a potion of wisdom on Geshniz's corpse. You can drink it to gain 5
int, but if you've chosen Allan as your alchemist, doing so will prevent you
from upgrading your alchemy garden a second time.
-The key to the chest on the middle floor of the mine office is sitting on the
left side of a desk on the top floor.
