Why not just rent a car? Seems like the easiest solution.
Megabus has regular trips from Buffalo to Toronto. $18 each way, but I don't think the times would work for you, and you'd have to get from the airport to downtown Buffalo.
If you could get to Niagara Falls, there's a ViaRail train from Niagara Falls to Toronto leaving at 2:06pm, arriving in Toronto at 4:06pm. The fare is $38.
By the way, I'm from Duluth, grew up there.