Fall Damage Rule sign you can buy on the gamemode tech-web for 800 buttcoins.
You only take fall damage from falling from a certain amount of blocks i feel like you take damage the same way the mace works where if you fall at a certain velocity you take damage and the higher you fall from the more damage / stuffing gets taken
The smallest amount of damage being taken should be 100 stuffing maybe but this could be changed with a smaller gamemode sign similar to the team damage multiplier block where you can adjust the height required take damage or how much damage you take from falling but the main “Fall Damage Rule” sign will be the main thing you need down for the other stuff to work