No, only DVC properties. However, Annual Passholders (and we do get $100 off on passes) can get nice discounts at WDW resorts, depending upon the season.
It's 25% and subject to availability. Just because they have a room for cash doesn't automatically mean there is an applicable discount. But if you reserve full price now and the discount comes on later you can get an adjustment but I don't THINK they automatically apply the discount if you don't ask. Others will likely no for certain about that last part.