Dawn of War Codex

How much % is it, and when exactly does it get applied?
Is it on a per model basis or per Squad?
Is it active while the unit is in the meleecharge? And if so what about units without meleecharge?
Or only when they are hitting something?

I guess it uses the same state that determines if a unit is tied up? But that is on a model basis... and sometimes units can shoot when moving towards enemys while being attacked in melee....

Thanks^^

Not sure if there's a definite set amount (it can be changed from unit to unit), and I'm not going to go through all of the units right now to check which ones have different values, but as far as I know, it's a 50% damage reduction while in melee combat a vast majority of the time (so when hitting stuff with a melee weapon - not in charge). It's on a per model basis and applies to most, if not all, infantry units.

Do Chosen PM have it?

Yep