In all of my experience thus far, the hotel will hit you with the full "rack rate" as fireworks says. I see you are losing the pull you had as a PLAT now that you are only Gold, so you would not even have the PLAT desk to call and beg for mercy with. Sounds like the gold desk told you to call the hotel directly...

Since you are talking about points, my guess is that this is a personal trip, so additional cost would not be something you'd want to cover. Are you trying to go during a major holiday or event? Typically, hotels blackout or have special rates. For example, during Super Bowl week in a city, it is not uncommon to pay 800 a night at a courtyard. I did that for a super bowl in DETROIT with some friends (Steelers won so it eased the pain).

I would call the hotel back and try to speak with someone else (did you get the GM or the front desk manager?) You may be successful arguing that whoever reserved the rooms for you messed up your stay - Is that the case or did you put yourself in this situation thinking you can squat?

Are there not any other hotels that can accomodate your entire itinerary? I would look elsewhere before trying to pull something that doesn't look like it could ever end good.

Just my 2cents