I know how frustrating that can be. Can you make your reservations tentatively and then apply the AP rates when they come out? You might also want to check on Courtyard Marriott LBV for the $20.03 rate Sunday- Thursday. I believe it starts the 2nd week of August. For that kind of rate, you won't be able to beat it anywhere! The hotel is VERY nice, clean, large rooms, very accomodating staff, nice pools, nice restaurant, and decent shuttle service to the parks. If you are going for longer than those 5 nights, you could cap off your trip by staying on property with the AP rates.
As for hours, we were there last August (stayed at CYM-LBV) and I believe that the MK closed at 6 or 7 pm except for maybe Friday and Saturday, when they stayed open until 9 pm. Epcot stays basically the same... Future World 9-7 and World Showcase 11-9, MGM closed at 8 pm and AK at 5 pm.
Hope that helps!