Even as it is written (καθως γεγραπτα). He quotes Psalm 44:23.

We are killed (θανατουμεθα). Present passive indicative of θανατοω for which see on Romans 7:4. Same idea of continuous martyrdom in 1. Corinthians 15:31.

As sheep for the slaughter (ως προβατα σφαγης). Objective genitive (σφαγης).