Demon King Level Butler

The author of a novel on the street was pissed off after reading some malicious comments, and then traveled back in time into a novel he wrote, where he randomly became the son of a demon king who didn't even have a role in the novel. But fortunately, there is no unstoppable path. His "Golden Finger" can gain points by changing the plot in the original text, and exchange them for abilities. How should the little devil survive in this Western fantasy world? (I don't know how to write an introduction. I'm here now. Let's read a few chapters.)