That was ME!!!!!
What I've found with
DCL interline rates is that you have to be willing to go and pay full price with DCL if you need more than 30 days notice. Generally they don't release interline rates until 30-60 days out, but if you are booked, they will either issue room credit for the difference or charge you the difference, depending. I have worked with interline travel agencies in the past, but honestly, I prefer just to do it myself...
Oh, and FYI - Disney World also offers airline Employee rates. They have a much, much, much larger window of availability and often you can get 50% off of rack rate (which is better than an AP discount). I paid $55/night including tax at AS Sports in May.
For all of these discounts, remember, you most likely won't find them during the summer, over holidays, all the usually busy times.