While the details we have for the saving Harry and the Last act are minimal, it's worth discussing strategies and possibilities. Good ideas the thread has makes Jacob's missions easier. The quest is fundamentally more narrative than mechanical.
If we want to get a bit brutal about it we could use Avifors and send the birds down Lupin's throat/peck his eyes, we could also make a surprise entrance with the Spongify + Flippendo combo on a wall of the shack and then repair it later in the fight, the goggles will even let us see through the wall so we're not doing it blind.
A bright lumos into the eyes could probably stun any enemy at least for a bit, especially since their eyes have adjusted to the dark.
Our patronus could also be used as a distraction against Lupin.
We could use diffindo to take out supports in the shack and collapse the roof on Lupin, then jump on his back while he's down and use the time turner, which probably puts us in the best position to flee once we arrive back in time.
We could break the window before Sirius goes flying through it so he's not as injured. Hell, since all we saw on the map is Sirius getting near Lupin and then going flying, if we time it right we could transfigure him into a rabbit and then flippendo him through it (assuming we broke it earlier) without him being hit or injured at all and no paradox would occur. If we do the spongify and flippendo thing then we could make it the wall Sirius goes through so that this manuvere is much easier.
As for capturing Pettigrew we could set fires in the forest to herd him where we want. Transfiguring his rat form into a bunny would be a good idea as well, make it bright white and he'll both be easier to catch, track and hit with spells. An immobulus would probably do quite a bit of good here as well.
If we see him in his human form diffindo his leg off, or, failing that, take his hand, fingers, toes etc so he can't run as a rat. These can be regrown, diffindo isn't a dark spell. A shot to the eyes would also make him next to useless.
If chasing after Pettigrew as a rat we could use avifors and summon birds that hunt rats and use them to get him, our goggles should make tracking him easier as well.
Uh, those are all the ideas I've got. Anyone else got any?