This is a pretty cool guide!
Although you'll have to thank RNGesus for the coke and mentos, not me. I think you just got really lucky with the item spawns, haha.
I've only tested out the cheat code on my computer and my phone, so I'm not too sure how to troubleshoot that. Sorry.
The pinch and konami code are the only two ways to active the cheat in-game, but the cheat toggle is saved as a boolean value under "NO_MILK_RESET" in the options.ini file (same directory as the save file), so if you're willing to do a bit more digging, I guess you could try flipping a 0 to a 1 somewhere.
This is a very nice write up! I actually didn't know how the save files were internally structured by Godot, so I enjoyed reading about your technical dive into save editing.
I definitely would like to figure out a satisfying way to incorporate size effects. Not too sure what'll come out of it, but I'm thinking about experimenting with some of the stuff you've mentioned as a starting point.