9. "How does the Talisman fit into all of this?
I'm sorry to say, but despite the superficial plot similarities of the Talisman to the Dark Tower (part of the novel has a boy travel across a blasted wasteland via train to reach a black hotel which contains the Talisman, "the nexus of all worlds and all possible worlds..."), it does not directly tie in. There are some small possible connections, the black hotel has weathervanes that feature sigils which might correspond to the guardians of Roland's world, early on there are mentions of numerous two headed animals (not unlike the animals Roland & Co. encounter outside Lud), at times Jack seems to be able to communicate via telepathy with Wolf, Speedy, and the Talisman itself (a la The Shining, The Stand and the Dark Tower books), and one character makes mention of other worlds, but it's clear that the world of the Talisman is not the world of the Dark Tower or any other of King's fictional Earths.
The world of the Tower has a feeling of being tremendously old, much older than our world. In the Talisman we are given the feeling that time in both Earth and the Territories is concurrent. There is also none of the cultural referencing that appears in Roland's world (the people in the Territories don't refer to "the Bible", but "the Book of Good Farming" and even though people had been travelling back and forth for decades no songs or bands seem to have made the lasting impression that "Hey Jude" or "ZZTop" did in Roland's world.) There is no reference to "lost" technology, like Blaine the Mono or even something as simple as guns and gunpowder, the people of the Territories are decidedly middle ages in lifestyle. The writing style is closer to "Eyes of the Dragon" than any of King's other books, but King has not (yet) made the connection there so I will not either.
Personally I think the Talisman was a huge writing exercise for King. He had some plot ideas and themes that he wasn't quite sure what to do with and so he wrote this book. But for some, as of yet unexplained reason, the Talisman didn't quite provide the release for those ideas that King wanted. Later he worked some of the same themes into the Dark Tower books (remember, when he wrote the Talisman he probably hadn't written books 2 and 3 of the Dark Tower.)
One sharp FAQ reader (whose name I have, alas, lost) kindly pointed out that Mr. Tower, the man who gives Jake the book on Charlie the Choo-Choo, makes a reference to the Territories. Several sharp readers have also pointed out that the grapefruit in Book 4 is eerily similar in appearance (and in the hold it has over people) to the talisman itself (along with the Palantir of Tolkien fame.) Perhaps my conclusion above is a bit premature. But I'm going to stand by it until King gives us a little more meat to work with.
Eagle eyed FAQ reader Jeff Woodman points out that Calvin Tower's mention of the Territories could just as easily work as a quote from Mark Twain, the last line of Huck Finn reads "But I reckon I got to light out for the Territory ahead of the rest, because Aunt Sally she's going to adopt me and sivilize me and I can't stand it. I been there before." Which would be completely in character for Mr. Tower. Of course it could be a double entendre as well...