It's been my dream for years to stay at the fort over halloween. We usually make it down every few years in mid-october for my Kid's fall break. My youngest is now a Junior in HS and in two short years I will FINALLY get to stay at the Fort over Halloween - probably with no kids - now that I think about it, I guess that's a bit creepy...oh well.
I would just keep calling, checking the website, etc. Every day!! 45 days out is a big cancellation time for packages. 5 days out is a big cancellation time for Room only. So there is a chance.
Also, if you can't extend, you can get off your site on the 31st, park in overflow and stay as long as you wish, even through the golf cart parade, trick or treating. You are a resort guest till midnite of your last day.
We do this often. Check out, hang at the resort, park all day, then hop in the truck and drive an hour or so North, stop for the night and continue the drive the next day.