For the rest of the night I'd leave a fan running aimed at the top of the water and leave the canopy off. Leave powerheads off, etc, just run the return pump and leave the AC on in the house.
If you have a heater in the tank, turn it to 76, this way the tank won't get too cold
Tomorrow, go to the store and get another thermometer, a digital one Coralife makes a cheap on, even ***** usually carries it.
Don't keep adding more ice at this point, it's been hours.
Your tank isn't that large. I think your thermometer is busted. If not, what I have suggested above should keep the tank at least stable until tomorrow.