There's unfortunately a really-difficult-to-pin-down bug in the game involving vsync, which seems to only happen on some machines. This is why your movement was so slow.
In case you decide to take another swing at it, I added this block to the game's page on Itch.
!!! IMPORTANT !!! IF PLAYER MOVEMENT IS SLOW the game may not be beatable. Try toggling VSync in your graphics settings (for Hero Mode.exe only, if possible).
Thank you so, so much for playing! :)