Thank you for playing my game and taking the time to leave a comment.
I agree it is perhaps too easy. Difficulty was hard to judge when it was only me and a friend playtesting. I find a lot of devs make their games far too hard because they have become experts while playtesting. I try to avoid that as I am aware that most people will only play my games once.
I like your suggestion of falling through the floor. I think I will add some floorboards that crumble as the player walks over them, eventually leaving holes that the player has to jump over. That should add gameplay tactics at the start of the game and make the end game more difficult. I think I will also make the ghost move faster as the game progresses.