Steve,from the sound of things your 'captive' nuts have broken away from the inside of the panel.
AFAIK they were welded to the backside of the panel.
To get the bolts out completely might involve a pry bar (or similar) placed between the hinge and the sheet metal to pre-load and jam the nut then try and turn the bolts out.
Don't go mad in case you bend things up though.
Only problem then is the nut,assuming you get the bolt out,will drop into the box section!
Maybe someone else will come up with a suggestion on re-attaching said nuts!
Good luck.
