We've released a brand new patch for HorrorVale - Act 1 that allows you to freely enter and exit fullscreen with the press of a key (F5) at any time, and without the stretching/blurry pixels. Go check it out for yourself!
Also of note: We only just recently noticed that here on RPG Maker net, the version of the game available was NOT HorrorVale Act 1, but instead a much, much older version of the game. So if you've downloaded that, we ask you to please download the newest version.