Another option is to rent a reservation for the nights you can't pay for with your own points. It's probably less expensive than a cash reservation. You could ask the other owner to have MS note your other reservation number on the rented reservation with a request to stay in the same room. Could turn out to be advantage if you wanted to take advantage of a dining plan for the shorter of the two reservations. Of course, you would not control the rented reservation until check-in.
If available, you can get a 25% discount on DVC resort reservations if you book through MS. This would probably be more expensive than staying in a value or moderate, but assuming MS can book the exact same villa type as your original reservation, you wouldn't have to move and the resort will see your reservation as one continuous DVC reservation.
It may be easier to get a transfer of points into your account if you are willing to take a transfer that is larger than your actual need.
Good luck!