See Note b, ch. 5.6. Having perfectly completed the work, he could sit down, and abide so, having done all; it is in contrast with the priests. They stood daily; he is set down 'for a continuance.' Connecting 'in perpetuity' with sacrifice spoils the whole force of the passage.
Not 'being,' nor 'having been,' 'sanctified', but the objects of this operation, those about whom God was doing this. As to date, 'we have been sanctified,' ver. 10.