I have a half-finished novel with a character who was — for a short time — a boxer. One of the reasons I gave up on it (for now) is that I have no idea how to write about boxing. You apparently do. I did my research, read about boxing in England in the time period of the novel, interviewed a successful boxer and a fight promoter, but couldn’t write anything that even I could believe. What I can’t believe in this story is that the insurance document in the safe would have survived the fire. You could fix that by saying at some point something about the fireproof safe. I like stories with happy endings, even if they are unlikely in the real world. Good job!