How can I save my gunite pool that is in danger of cracking with freeze guard disabled by power outage?
Jump in and break the ice periodically. Minnesotan up!
Seriously, walk the perimeter on a regular basis and bust the ice up with a shovel or other heavy tool. Unless the ice gets thicker than say a half inch across the entire surface it won't cause damage.
Covering it will certainly help. You have a lot of heat in the ground, so if you insulate the top it'll stay much warmer. Pull your cover over it and throw all your extra laundry on it. Dark colors absorb solar heat.