I know it's loosely based on historical events, but does it accurately reflect the level of violence/ depravity of the times?
I'm not qualified to answer your question, but I too have wondered the same thing. I found the world that Cormac portrayed in the novel extremely captivating. One thing that helped quench my thirst to know more was Notes on Blood Meridian: Revised and Expanded Edition by John Sepich. It is a great resource if you want to find out more about the people, places and events that inspired McCarthy's writing.