The first candelabra lit by Alan has many spiderwebs between the candles. After he approaches the mirror, the webs are gone.
About 21:00 minutes into the film Alan strikes a match and lights three candles of a 4-candle candelabra, then blows out the match. They cut to Alan, and all four candles are lit.
Alan is supposed to be fatally impaled by a spike (which is what we see in close-up), but the spike in the swinging gate could only hit him tangentially. His body remains upright but there is no embedded spike to provide the necessary support. (In any case a supporting spike would need to be not in the gate but in the railing behind him.)
All victims killed by strangulation die too quickly. Strangling someone takes a lot more time than a few seconds often shown in the movie.
During the opening scene when Alan Foster enters the tavern, the Four Devils, a crew member is visible in the reflection in the doors glass window. He's using a small hand held device and generating additional smoke for the scene.