When Greenwood shows Matt the warrant he has for the four men, the quality of the paper, and the writing on it, is better than when the warrant was written.
German Shepherds weren't introduced to America until 1907.
Actually, Jack Elam's character unhooked the dogs ONE AT A TIME, not together. So there could have been some time in between their charging at "Thad."
The three dogs are released at the same time to go after Thad, but they reach him one at a time, leaving enough time for Thad to defend himself from each one.