Matt makes several references to "General Custer" during his conversation with Chester at the end of this episode. In fact, Custer during his assignment to the 7th Cavalry was only a Lt. Colonel. He had held the brevet (temporary) rank of Major General during the Civil War, but returned to his permanent rank of Captain at war's end. Upon formation of the 7th Cavalry at Fort Riley, KS, he was promoted to Lt. Col and assumed command of the regiment.
A hand salute is not to be rendered indoors. When an officer comes into a room a person of lower rank comes to attention to show respect. And the rules governing this were only recently changed to allow someone in civilian clothes to salute. They have to be a veteran and have cover (a hat). This was done to allow veterans to render a salute in flag ceremonies.
Matt opens strolling thru boot hill with one grave marked "1882", yet the story is set no later than 1876, the year of Custer's last stand. It may not be a goof because the boot hill musings never have had anything to do with the stories and could represent Matt's reflections years later.