The Frisco KidGoofs
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.
Errors in geography
When Avram chooses not to ride his horse due to it being the Sabbath is a common belief among Hasidic Jewish people, who won't drive or operate anyhing with electricity on the Sabbath. Given the situation Avram was in when the men where chasing him and planing to hang him and Tommy. A Jew would be allowed to ride or to drive a car or do anything to get away. Since another force is threatening his life.
Avram warmly shakes Mrs. Bender's hand when she welcomes Avram. Since Avram is an Orthodox Jew, He is in fact violating the law of "Shomer Negiah" which states that a man or woman may not touch a member of the opposite sex, unless it's your wife or immediate family member. Since Mrs. Bender is neither, he would not be permitted to shake her hand or touch her in any way.
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.