Any 2h weapon should be able to "Cleave" because you are just swinging the weapon in a big arc in front of you, it doesn't matter if it is a sword/spear/staff or club if it is 2h it gets access to "Cleave"(maybe rename this?).
I doubt this. The weapon should be really sharp in order to be able to cleave through mutliple bodies. With a blunt weapon perhaps a kind of domino effect could be accomplished, but the adversaries should stand in a straight line for that, not an arc.
You are focused on the name "Cleave" IMO.
You are not actually cutting anyone in half to be able to hit the next target in line.
Have you ever watched the show Forged in Fire? One test they do on blades is swing it through say multiple stalks of bamboo in a row. While a sharp blade might cut through the entire row, a duller or blunt blade might only cut 1-2 stalks before continuing on to just smash its way through the bamboo but not actually cut it. Even a dull blade that doesn't cut through the bamboo at all can smash through it and cause snapping, a 2h blunt weapon would "Cleave" in the same way...by causing blunt force trauma to all targets in the arc.