I'm on Windows 11 Desktop, and using resolution of 1920 x 1080. Here's a screenshot:
The only thing I changed is renaming the inner folder to Game so Renpy can run it, and putting the game in the same folder as my other renpy project. though I re-downloaded and it's still the same thing. But I think I figured it out. in the message_viewport, you defined the ysize to be 750, so I removed that line and it somehow auto-scaled on its own with the correct ratio O_O