Here is where I think your numbers are coming from. First, you can not "stack" the discounts so you would not be saving an ADDITIONAL $960 for the DP on top of the Fall discount. You gave up that room discount to get the FD. So now you are saving $959.60 (based on 2A2C I assumed from your numbers) on the DP. You are also paying VALUE season rates even after regular season begins on 10/2. There is a $17/night difference between regular and value season prices. So 17 x 9 nts x 1.125 (the 12.5% tax rate) = 172.13 room discount. $959.60 + $172.13 = $1131.73 less $10 change fee charged for pkg changes made after 2 weeks prior to arrival date...$1121.73 total savings. This is off only .67 from your numbers and could be due to the fact that, I think at least, there is a slightly differently tax rate at POP since it is in a different county. Anyway, we are going around the same time and our pkg priced out to the penny by using value season rates during our entire stay along with the FD.
And the $53/night is probably a per person pkg rate based on 2A, 1J, 1C which is usually how they price the examples for their pkgs. It does not mean that the actual room rate you are paying is a flat $53/night.