This is an overly literal meaning of the word wizard. Are you maybe not a native English speaker? "Wizard" in English not only refers to the magical being that performs sorcery, but it can also refer to someone who highly skilled and can put on a performance. A math wizard is someone who solves difficult equations with grace and style, almost like they have magical insight. (Wizard also has this double meaning in Japanese as far as my dictionary tells me. There is a Professor Layton vs Ace Attorney soundtrack title for when Phoenix is stomping somebody in the courtroom called "The Courtroom's Magician." Masumi is an English speaker anyway.) When Shinichi used "Shiranpuri" in Red vs. Black to make everyone but the culprit sit down, you can call that moment a "spell" from a detective wizard. Shinichi also has the habit of turning the culprit's tricks into his own performances like they are acts in a magic show, like having Takagi hide invisibly in a pool and then suddenly appear on command, or make Sera appear from a chest of fruits. Wizard absolutely fits Shinichi's "explain the trick, reveal the culprit" style, especially if you are an impressionable child like Masumi. With the right sort of trick in the past case of waves, I can definitely see Shinichi doing something that appears to be magical to show the truth.
About the rest of your post, you've made a bunch of suggestions but haven't tied them together into a coherent theory. It was like reading a stream of consciousness rather than organized thoughts. Maybe I can help you sort it out by spinning the argument around: 1) Do you have any evidence that shows Conan is not the Wizard? 2) If the Wizard is the unknown child, do each of the wizard clues and their timing make sense?
Edit: To make life easier, can anyone help me list the chapters where wizards are discussed (Post Sera)?
Manga Volume 81, File 11 (861), pg 15-16: "Just like Magic" Middle bro asks if Sera has met the wizard. "You could say so"
Manga Volume 83, File 2 (874), pg 8: "The Red Past" Sera's purpose in coming to Japan is to meet the Wizard once more.
Manga Volume 86, File 1 (905) Ran has a flashback. Child Sera says "You are a wizard, right?"