It really has been a long time since you were last there, hasn't it? The first week of October will see carry-over of Free Dining guests who began their vacation on or just before Sept 30. There are some school districts that have a fall break in Oct. The F&W Festival, which has become incredibly popular, will have been in full swing for over a month. Then there is the MNSSHP, which also draws crowds. A complicating factor with the Halloween parties is that they close the park to non ticket holders after 6:00, greatly reducing ADR availability on those days.
It's been a fact of life for many years that if you really want to eat at a specific restaurant, and especially if it's a popular place like BOG or Ohana, you need to get you ADR as far in advance as possible. Only 70 days out? All you can do is haunt the reservations pages and hope for cancellations. Or try the TouringPlans reservation finder.