Although brother Frank did join Quantrill, there is no evidence that Jesse, less than 16 at the time, ever joined the guerrilla raiders in Kansas.
Seems most of the actors are using handguns invented after the Civil War. Quantrill is not using French Pinfire revolvers and his uniform is the wrong style - incorrect button pattern for a Confederate Officer.
The reviewer did not take in that the story is a fictional so the goofs he mentioned are not important. When you write a fictional story but having it in a real historical place you can use whatever characters that you want.
Kate is inexplicably and obviously shown wearing a 1950s plastic hair comb while she and Jesse kiss.
Around the 17:00 mark of the movie, Quantrill is speaking to his group of men. While he is doing so, a telephone can be heard ringing twice in the background.