Several of the rifles in the sheriff's rifle rack are Winchester 1893 models. Since the films's setting is from the late 1870s until mid-1880s, those model rifles should not have been invented much less distributed.
At the theater the band plays an introduction with the conductor playing a violin while alternately using the bow as a baton. Near the end of the number he plays the violin for three notes with no sound; then, he holds the bow as a baton and the three notes are played.
(at around 18 mins) Dingo's widow and Dooley are in front of the marshal's office and Marshal Ware hands Dooley Dingo's gun and personal effects. Dooley throws the gun and belt onto the ground and later he throws the five Double Eagles on the ground at the same spot. After they leave, Marshal Ware picks up the five coins, but the gun and belt are not on the ground and were never picked up.
When Dingo's effects are presented to the Marshall in his office the holster rig and pistol are completely different from the rig shown in the closeup at the beginning of the film as Dingo rides into town.
The knife thrower who attempts to kill the sheriff tosses his knife with near -perfect accuracy (he missed) from roughly 50 feet away. However, not only is the knife not a throwing knife and thus almost certain to miss, the distance is simply too far for even the best of knife throwers to hit anything with any measure of success.
The $100 dollars in gold that Dingo's brother throws away represented for many a year's salary. It's unlikely that he would have done so, even if he was ashamed of its origin because it is probable that he never would have seen that money in once place in his entire lifetime.