Do you think Piggy is fully aware of how far from “civilized behavior” Jack and his followers have strayed?

No, I believe that Piggy never lost hope in the morality of the group as a whole. Up until his death, Piggy still believed that he could talk to the boys.... that he could reason with them and make them understand. Had he understood, he may have used his own rationale to avoid the situation that led to his death.