Spruce and Mansfield are the major base lodges. The others are smaller lodges.
Yes it's a one time charge, per person. But if you ever come back you use the same card.
You can check craigslist for lift tix, I've seen a few multiday tix for sale recently in Boston for pretty cheap. Also, I just came back from stowe earlier this week (it was awesome) and I got my tix thru the inn I stayed at, was less than $130 for a 2 day pass, and they were disposable so I didn't have to pay the $5 fee.