Is Points + Cash available for the 7 nights you want ? If so, and if you have the points, reserve that space and then cancel your current reservation. If P+C is available but you don't have sufficient points, I suggest you call and have an agent help with the cancellation and new booking. I usually see points back in my account instantly after cancelling a reservation, but I wouldn't take a chance given how difficult it is to find P+C rates.
I don't quite have enough points, but when I check those dates, it shows me the total for seven nights (while telling me that I don't have enough points). Does that indicate that P+C is available? I would think so...