Have you tried shorter stays? different start dates? Have you checked 3rd party websites like hotels.com or expedia.com?
October is a relatively popular month. Many schools have midterm breaks in October around major holidays (Yom Kippur October 5, Columbus Day October 10). You also have fall and Halloween decorations and events, as well as the Food & Wine Festival. Plus there's the Gartner Symposium which runs from October 17-20, with some attendees arriving early to take advantage of special convention rates and free time before the meetings commence. Lots of demand for rooms in October.
People do cancel, so things can become available. It's probably a low percentage but it only takes once to cancel and you to be stalking at the right time (or if it's DVC you have a waitlist in place).
Just keep checking. We went last year around the 50th anniversary and rooms started to become available as we got closer to our dates. Especially around the 30 day mark when final package balances are due.