This is not the forum to give you the "simple" answer(s) you seem to be looking for.

You say you are in Pa. but later quote N. Carolina law.....................

Read your State's statutes (or the State you are in)..... read case law....... take a seminar with a lawyer who practices in your State and specializes in firearms and use of deadly force.

First off what you are asking about is..... the justifiable use of deadly force..... not "justified to kill".... to stop a threat of death or serious bodily injury.

Death may result from the use of deadly force......but I've never seen a statute written that justifies....... the outright "killing" of another human being.