Soldiers at West Point are to be placed under a protective curfew beginning at "0600 hours" (6 AM) the following day of Landor's visit and interrogation. The United States Army did not adopt 24 hour time until 1920.
At multiple points in the film, bird sounds were added as background sound effects, including the Eastern Kingbird and Wood Thrush. Neither of these birds is found anywhere in the US, much less as far north as New York in the middle of winter.
West Point is on the western shore of the Hudson thus any scene showing the current would flow from left to right. When the hanging body is found the flow is from right to left.
The ceiling/floor/timbers on the lower level of the ice house would be constantly damp from the melting ice on the floor above. This is further evidenced by the constant sound of dripping water when Landor investigates earlier in the film. As such, it is not realistic that fire would spread as quickly as it did, if in fact at all, when the candles are knocked over during the climactic ritual.
Edgar Allen Poe was born in Boston, but from the age of 2 to college age, when he attended the University of Virginia, he was raised by a couple in Richmond, Virginia. It is very likely he spoke with a southern accent of some nature.