Aside from the catastrophic or complete kill, which render the tank both unusable and unrepairable, there is always the mobility-kill because engines, tracks, or running gear get damaged, the firepower-kill because the tank is no longer able to function e.g. because gun or optics/optronics damaged or destroyed and the mission-kill which are all other reasons why the tank can no longer function as intended.
THe link on that gun-fored 125mm ATGW says:
Now, does that mean 750mm total (including ERA) or 750mm behind the ERA (so after that has been penetrated)?
The first warheador precursor charge won't penetrate any armor. its only job is to destroy the explosive in the ERA tile so that the second or main warhead can properly form it's shaped charge jet.