People shoot more than six bullets out of six shooters, without reloading.
Around 01:08:04, we can see Eli is attached to a tree with a cable.
The kids take the pistols from the sheriff and Rattlesnake, but later Jenny finds them and sends them off. She is left to unload a shotgun, yet the kids never stole a shotgun.
During the third incomplete duel between the sheriff and Rattlesnake, the sheriff sinks totally in the mud, but appears on later scenes. It is not explained how he got out of the mud.