OP, the way you have structured your trip with a few days in each place makes it expensive - it would be cheaper to spend the whole trip at Disney or Universal. Tickets for MNSSHP are not cheap either, but if you have purchased them already, then that part is done. The PP is right that you can enter MK at 4 pm on the party day - you should get a lot done that day.
I would cancel the beach and spend several days at Universal. If you stay onsite anywhere but Cabana Bay (and there is availability if you look for more than one night), express passes are included (Sapphire Falls also won't have express, but it won't be open by October). Cabana Bay is about the same cost as your beach hotel and gives you early entry but no express pass - if you stay for a few days, you could drop the express passes (although tickets would be more for more days). AAA usually has good rates for the Universal hotels, but you have to call to get the rates - they don't appear online.
I would drop some of the Disney TS meals - you don't have that much time there. T Rex and Rainforest Café are pretty similar, and going to Downtown Disney will eat up a bunch of time. I would also cut back on the breakfast ADRs and eat breakfast in the villa - do you have a kitchen?
You can make a dent in the budget, but I don't see you saving $1500 unless you are willing to restructure it completely.