The buy 4, get 3 deal is for packages only. You would have to purchase a minimum of a one day base ticket. It is not possible to book room only with this deal.
I think that your numbers are off.
If you go to Disney's website and plug in 4 nights @WL in late July (std. view) for 2A/1C, 4-day MYW base tickets, the price comes up $1746. Assuming that these rooms will be included for those dates in the extended 4/3 deal, that's the price that you would pay for 7 nights/7-day MYW base passes.
Odd - I got those numbers from Disney's site. Only difference was it gave us 5 day park hoppers.
And it probably also automatically added WPF&M as well. That and hoppers will add an extra $346 to the cost of your trip!