The Play, Stay, Dine Special Promo has a minimum stay of 3 nights. The example Disney uses shows a 5 night stay, but you don't have to stay 5 nights. If you want to change resorts midway through your vacation, you will have to make a separate reservation. As GaDisneyDad wrote, "split stay" is an internet term and not an official Disney policy. To Disney you would be making two completely separate reservations.
I have not looked into the P, S, D promo, but most promos let you book tickets of up to 10 days even if you are staying fewer nights. The ticket minimum will be in the info for the promo. If this is true of P, S, D you could book tickets for your whole trip with the P, S, D reservation and then book a room only for the AKL nights and pay out of pocket for food (or book a ticketless package with a paid dining plan).
If you wanted P, S, D for the AKL portion of your vacation as well there would have to be a room available under the promo and it would include tickets (the Play part) which would probably make the promo no longer cost effective.