Tides are indeed the tricky part. They do all sorts of funny things around the Strait. You really want to shoot the gap on slack tide; if you get wind against tide it can get really messy very quickly and result in sea conditions far worse than just wind. I would skirt around Fishermans Rock as well, as the upwellings there can produce strange conditions.

It would be worthwhile picking up a copy of paper chart NZ 206, the NZ Tidal Stream Atlas, as it gives you a decent idea of the flow direction and strength in different areas of the strait at given times and will help you plan for a window. Unless it's a glass off you'll probably need a good hour or so window.

Course-wise, from Tory I'd be running it pretty much straight at somewhere between Makara Beach and Pipinui Point (Boom Rock) and then turning up the coast once you're in the lee of the island. There are some gnarly rips/turbulence that form around Ohau Bay southward - which also means don't get tempted to follow the ferry too far across, as they will pass to the south of the real doozy (Karori Rip) which will ruin your day if you end up on the wrong side of it.