I'm thinking about your theory. Trying to evaluate its merits. There does seem to be a theme about monsters not being what they seem. Shoot, even Kore is similar to Frankenstein's monsters in some ways but yet she's clearly not a monster at all.
However, there's a big stumbling block I have with your theory. Picard talking to Renee has nothing to do with monsters and would not teach him the lesson that you're describing. The coma dreams he had touched on that, but that was an unintended consequence of the mission.
So, while I think there is a theme about monsters, I don't think that's what Q is trying to teach Picard. Picard talked to Renee but it was very much him passing wisdom on to her, not the other way around.