Update: I kept the system on fan-only the whole day yesterday, and I turned it back to cool at about 5:00 PM. It had reached 80 degrees by that time, and I camped my children out in my playroom (on another floor) to sleep. B"H, the system seemed to be working fine, and although I lowered it in increments, giving it a break every few degrees, it was back down to 70 by midnight.
I'll keep an eye on it, but hopefully it's back to normal, and DDF saved me money once again.
Thank you!