When Sir Malcolm takes Vanessa to the shanty town, he insists that she wear a face mask because "cholera is rampant here". Face masks protect the wearer from airborne diseases (transmitted by inhalation). Cholera was identified as a waterborne disease (transmitted by drinking contaminated water) in 1854 - wearing a face mask would provide no protection.
When Sir Malcolm and Madame Kali are at the pistol target range, during a close-up shot of Madame Kali's pistol, the crimped noses of the blank rounds are clearly visible in the chambers of her revolver. She is obviously firing blanks.
The action takes place in 1891, yet on the shooting range Timothy Dalton's character produces a Mauser pistol that wasn't made until 1896.