In "The Pit and the Pendulum", how does the darkness magnify his fears, and what issues will he have when rescued?

The dark
in the initial torture sequence makes him wonder if he might not really be dead.  It is so dark
that he has trouble realizing if his eyes are open or if he is conscious.  However, the
narrator's senses return.  But since he is in complete darkness, a new fear creeps in.  What if
he is buried alive?  This is his worst fear.

The narrator, however, is
eventually able to quell his fear and begins to make sense out of his surroundings, which, of
course, is exactly what the inquisitors expect, which leads him into his first
torture.

The narrator is facing a whole host of issues after his rescue.
Imagine surviving nearly falling into a pit where you most likely would drown.  Then you find
yourself tied down and nearly cut in half.  Finally, you are almost roasted alive.  So some
fears the narrator might face are many. Paranoia.  Fear of the dark and of rats.  A fear of
being alone.  Nightmares.  Depression.  Any of these would have been real issue for a survivor
of such a traumatic experience. 

However, given that this story is told in
the first person point of view, the narrator is obviously telling this tale after the fact, so
he has to be adjusted enough to recount this harrowing experience to us, the readers.