Glad you got it done... From the number of responses, I can see that everyone here likes a challenge... I had to remove several headless screws from the battery
area behind the rear seat... the previous owner had placed a board over them with holes drilled in the underside to protect the battery
from the jagged posts... I finally "worried" them out with a combination vice grips and perserverence.
For your problem I was going to suggest carefully applying glue in the outside crack between the nut and the housing to hold it enough to unscrew it... probably wouldn't have worked, but like I said... you definitely got the group thinking...