A bit late to plunge into discussion, so I won't do it. But I would like you to take a look at
The Bridge of Khazad-dûm by the
Barrow-Wight
It does not discuss the chapter per se, but deals with interesting option of possible merchant traffic and economics (to be more precise: how entire kngdom is supposed to get the stock it needs to feed inhabitants via single narrow bridge?)
Gandalf and Balrog were discussed in many threads. Among the recent, I may recommend
Wielding the Flame of Anor by
Keeper of Dol Guldur
Balrogs per se:
Post #33 of
One hand tied behind their backs by
Mithadan
cheers