This is not supported. The book collector is only talking about people being able to track down the out-of-print books they already want. We don’t know about identifying new books.

This is not supported. The book collector never refers to people trying to find books that are in print, so we can’t compare with people who try to find out-of-print books.

This is strongly supported. In order for Internet search capabilities to increase the demand for out-of-print books, it must be the case that being able to more easily find these book increases the demand for them. And increasing demand definitely means affecting demand!

This is not supported. All we know is that the Internet makes it easier to locate out-of-print books. We still don’t know how many of those books can actually be found, just that it’s more than would be found without the Internet.

This is not supported. The book collector only says that the Internet makes it easier to locate out-of-print books, but doesn’t indicate that it’s necessarily impossible otherwise.