The broken walls are a really interesting addition. But I wonder if they highlight an issue in how the game conveys hidden information?
I assume that to avoid visual clutter, you don’t want to have fallen monsters all over the place. But equally, if you left dead monsters only where their position/orientation/etc was relevant, it might give away too much.
What if you had a toggle button or mouseover area on the bottom bar that just showed where the monsters you’ve killed were? It would allow players to make deductions without having to rely on remembering what they’ve killed. I guess an alternative would be a more elaborate marking system that could mark-up uncovered cells and distinguish between possible values and certain values (eg placing a purple 4 on two squares would denote the other gargoyle is here or here)