dop2000 , anyone reading this.
Ok. I think I understand now. Firstly the button actions and movements not working--- that was fixed when I reset every single image point. So, for anyone new like me reading this: image points have an extreme effect on all aspects of platformer functionality (probably common knowledge, haha)
As for sprites not loading, I haven't solved that. But I'm assuming that they're just not loading right due to something about where the original file is saved, like you were saying-- a damaged file. So I'll look into that.
Anyway, thank you.