How we cite our quotes: Citations follow this format: (Paragraph)
Quote #4
That had been the end of his vigil, of his gallant attempt to conquer the ghostly tradition of the place, and never, I thought, had apoplexy better served the ends of superstition. (31)
It’s clear that the young duke who died had been involved in a project similar to the narrator’s: proving the red room isn’t haunted, by making it through the night. The narrator admires the duke's project (he thinks it was a "valiant" attempt). This gives us insight into the narrator’s own motivation. It’s also worth noting that the narrator explains the young duke’s death in a way that excludes any role of the supernatural. The narrator claims the duke had "apoplexy" and fell down the stairs. We get the sense he resents the fact that the duke’s death has been ascribed to the ghost, and used to support the very superstition against which the duke fought. What’s apoplexy, by the way? Well, it can be a lot of things: a stroke, a hemorrhage, or just a fit of some kind. Maybe, in this case, it's a fit caused by fear.
Quote #5
My mind, however, was perfectly clear. I postulated quite unreservedly that nothing supernatural could happen, and to pass the time I began to string some rhymes together, Ingoldsby fashion, of the original legend of the place. A few I spoke aloud, but the echoes were not pleasant. For the same reason I also abandoned, after a time, a conversation with myself upon the impossibility of ghosts and haunting. (34)
Even as he’ starting to suffer "considerable nervous tension," the narrator is still sticking confidently to his rejection of anything supernatural. That’s his reason talking, and it’s just as sure of itself as ever. It doesn’t seem to be having much of an effect on his fear, though.
Quote #6
The one in the alcove flared in a draught, and the fire-flickering kept the shadows and penumbra perpetually shifting and stirring. (35)
This is important bit of information: it tells us there’s a draft (the British spelling is "draught") in the room. Moreover, this draft seems to be most pronounced in the alcove. Could that be what causes the alcove candle, and possibly the others, to go out? At this point, the narrator’s quite happy to explain the candles’ behavior with the draught.