Its available all year round at Fort Wilderness. In October it should take place at 7:30 pm, though if you get there a little earlier Chip and Dale usually come out and play games with the kids before the official start time (though that's not guaranteed). They will light the fires at 7:30, start the sing-a-long at 8 pm, and start the outdoor movie at 8:40. You'll want to double check on those times. If you have any specific questions, feel free to pm me or hop over to the camping forum and ask.
Yes, all of it. There is music and entertainment before Chip and Dale come out. Often they have a game of bingo beforehand (before the music). The making s'mores part is "blah" not much to it. The two campfire rings are tiny and kids cross over the barrier to get closer. As an adult there without a kid, I wouldn't do the s'mores part.
Yes, it's free! If you google "fort wilderness resort activities calendar" typically kennythepirate.com will have the resorts activity page uploaded. The Disney website shows that showtimes are unavailable. So, you'll have to check back when it's closer to your time to go via that route ^ or call the hotel to see if it's offered. As far as I know, it's seasonal.
You can bring your own stuff for s'mores or purchase a pack there!