In a conversation between Avram and Tommy there is a reference to the country of Czechoslovakia. The film is set in 1850 but Czechoslovakia was established in 1918 as a result of WW1. The territory was then called Bohemia.
The movie is set in 1850, and in the early scenes (probably in
Pennsylvania with the Amish community) there are barbed wire fences lining the roads. Barbed wire wasn't invented until 1873 (earlier versions might have been available but were not mass produced and certainly not for that long of a stretch) and was intended mainly for the western United States, not the eastern half.
Several characters use the Colt Army .44 cal pistol. This wasn't developed until 1860. Also, during the final gun fight, Matt Diggs gives the rabbi a Remington New Model Army .44 cal pistol. This didn't come out until 1858.
After Tommy shoots the first fish when the two main characters meet, he asks Avram how hungry he is. After Avram replies "Ah, I'm pretty hungry" Tommy takes out a long gun to shoot another fish. There is the sound of a lever-action rifle being cocked, but the gun he is holding is a side-by-side shotgun with exposed hammers. The sound of this gun being cocked would have sounded more like a revolver with the hammer being pulled back.
The Jewish Sabbath does not necessarily end when the sun goes down, but when it gets dark which could be up to an hour later. Also, an observant Jew would not be able to travel outside a city on Sabbath, even on foot, for more than 2,000 biblical "cubits" (~1,000 yards) from the place he was in when Sabbath began. Therefore, Avram would not have been willing to travel, leading his horse, on Sabbath. It is also forbidden to carry on the Sabbath in a public domain (such as a road), or to make one's animal carry. This is another reason why Avram would refuse to travel.
In Judaism, a person is not only allowed but required to break the Sabbath if a person's life will be in danger if they do not break it. When the posse is chasing Avram and Tommy, both their lives are in danger, and Avram would have had to have jumped on his horse until they were out of danger.
In the first scene where Avram is thrown from the wagon and proceeds to pick up his belongings thrown out earlier, after picking up everything he finally gets to his suitcase and exclaims, "This, you couldn't throw out first?!". In fact, the suitcase was thrown out first - that's why he got to it last as he backtracked.
After reaching the Coast of California, Avram and Tommy must travel a day-and-a-half North to reach San Francisco. In one of the next scenes they are shown riding with the ocean on their right-hand side. That would have had them riding South.
When Tommy is giving Avram directions to San Francisco, he says to take a left at the ocean and keep it over Avram's right shoulder. But when Tommy and Avram both arrive at the ocean, Tommy points to the right to indicate the direction to San Francisco when he should have pointed left.
The mezuzah on the doorpost of the Jewish home in San Francisco where Avram drops off the Torah is facing away from the inside of the home. This is incorrect. The top of the mezuzah should be facing towards the inside of the home.
When Avram and Tommy are "running" from the posse, Avram waits to get on the horse until the sun goes below the mountain, yet when the pair begins to ride away, they and their horses cast full shadows as if exposed to sunlight.
After the final gun fight scene, the rabbi drops three balls from the rear of Matt Diggs' pistol. With the 1860 Colt Army .44, the balls must be rammed into the front of the cylinder with the loading lever. They will not fall out.