If you have a a split stay, how can you link the 2 hotel reservations so that when your 60 day ADR window opens, it’ll open up the entire vacation and not just the length of your first hotel reservation?
If it is the same room type/ resort maybe Disney can merge them (they can for DVC). Otherwise, they cannot be merged and you have two 69 day windows.
The other thing to do would be to make a fake reservation for all the days, make reservations. Then once your last reservation is with in 60 days, cancel your fake reservation.