0 pressure and running it means damage. Simple as, unless you are some how very very very luck.
I wouldn't run a car with 0 pressure.
You need to get the oil pump off and try another, Id remove a crack cap too and look for scoring on the crank/bearing. If they haven't had oil on them they could be buggered.
Iirc the pump is 8 bolts. Then a philps to get the pump its self apart.