Since I think I am the only pipe smoker in the game:
Pipe smoking.
Modern pipes and tobacco are typically sold in sizes of 2oz 4oz or 1 pound. (Unless you are buying in europe where it is 50g 100g or again, a pound. I don’t know why it doesn’t go to a kg it just doesn’t.)
2 oz will typically hold, in a modern pipe, about 12 pipefulls give or take. Older pipes like the one What Exit linked to will hold a little more than half of a typical modern pipe. So you get about 18 or so pipes our of a 2 oz tin with that type of pipe. It would probably take between 15 and 30 minutes to smoke a pipe that size, and a modern size pipe between 30 and an hour. Really skilled pipe smokers can make a normal modern pipe last for 90 minutes or so, and then there are larger pipes, but we won’t get into that.
I don’t know more than a handfull of people who would smoke more than 3 pipes in a single day. If someone wants to extrapolate from there how many pipes would be smoked per person per day on this journey, you are better people than I am. But I don’t think 5 lbs for 2-4 people would be too much for a few months, particularly if there was a bit of leather around to wrap the tobacco in to help keep it fresh.
As for size. A pound of bulk tobacco comes in a bag the size of a medium sized potato chip bag (not a single serving bag, but not a giant party sized bag either)that is stuffed full. 5 of those bags should be easy to transport. I am not sure what kind of container it would come in though in our world. Ceramic pots of some sort would be my guess.