Thanks for the feedback.
To be honest, we bit off more than we could chew, hence had to reduce the number of levels and wrap the tutorial in one level.
Secondly, the enemies shooting physics based objects was intended. We did try to resolve the bug where you could "cheese them by standing just next to a corner that they can't fully shoot around and shoot the edge of their hitbox", but we were short time, and had to leave it as it is.
Thirdly, "Well they're ghosts. They're well known for going through walls!", this is a great idea, we didn't think of it LOL, I might update the game after the jam and implement this.