The cabin that the couple lives in is far too luxurious (by the standards of that time and place) to be credible. Multiple glass windows, multiple glass lamps (that use kerosene, which in turn has to be bought at the store many days away in town), multiple feather pillows, doors with real hinges instead of leather strips: all of this indicated more wealth than the couple could have earned from their farm. And a non-wealthy couple wouldn't have been living out there.
The double-barrel shotgun Lizzy uses requires percussion caps, but whenever she fires it or prepares to fire it by pulling back the hammers, there are no caps. Without them, the weapon is inoperable.