Part 1: Pick Pocketing Malformed Defias Drone.
-So I had the same problems as a few of the other commentors in that he was resisting my pickpocket. Here is what I found out:
1. When he has the key on him, he will have this sparkling glow around him. If he doesn't have this glow, he doesn't have the key and you need to kill him or wait for him to reset (not sure how long this may take).
Part 2: The other comments said it well... But to make it easiest. I just died, then ran to the top as a ghost then ressed, sapped, and looted... THE KEY YOU LOOT HAS NOTHING TO DO WITH LOOTING THE CHEST! YOU NEED LOCKPICKING 75!