How does poe create an unsettling atmosphere with stylistic devices in the passage above?

Well  he uses effective imagery throughout his stories. He describes the objects in the settings and their importance. He often emphasizes on what they symbolize as well. For example, in The Pit and the Pendulum, the candles melting in the cell represent the prisoner's hope of survival which also diminish. The pendulum, like the pendulums in grandfather clocks, represents a symbol of death. 

Sweetness and love, happiness etc.