Also wondering about the robber stopper used on a gallon jug. I'm assuming I can find these at Home Depot, do they have the hole on them already for the blow off tube and airlock or would I have to make the hole?
A gallon cider jug will take a #6 or a #6-1/2 stopper. Your LHS should have both. Also, you will want to use 5/16" tubing for the blowoff. 3/8" tubing won't fit in the holes in those stoppers.