That he should offer himself often (hina pollakis prospherēi heauton). Purpose clause with hina and present active subjunctive of prospherō (keep on offering himself, like Heb 5:1, Heb 5:3).
With blood not his own (en haimati allotriōi). So-called instrumental use of en (accompaniment). allotrios means “belonging to another,” “not one’s own” (Luk 16:12).