I can fully relate to lesson 3! Especially in the last few hours I kept on sinking time into problems I could just not assess anymore instead of pivoting to something else. Very important, indeed :)
And to lesson 2: This is probably one of those things that need to be learned by hard. Because in a professional environment this is very usual. I don’t know much about the 3D-pipelines of other engines but in Unreal it usually is not a big problem, once you know where the limitation of pre-viz are and how to keep world scale throughout the whole thing. I guess for Unity it should be the same. Can’t think of a reason why it should not be in Godot, too. What have you been using? And maybe that is something to give Kay feedback about :)