Air stone is better than just tube. Creates more surface area, which means more gas exchange. Deeper is better, as it will create more water movement, and increase the contact time which again, means more gas exchange.
For temperature is the problem that's it's cold out or that it's hot out? Too cold is safer than too hot but ironically too hot is much easier to fix without power. It sounds like it's too cold... you really need to insulate the tank as soon as the power is out in cold weather; I have a set of foam I use that I tape to the sides if powers ever out for more than a few hours. Since it's probably too late for that... if you have a way to heat water - a gas stove that still works when the power is out is probably best, but a camp stove outside will do - you can take about a gallon at a time out of the tank and boil it. Mix it with several gallons of tank water in a 5 gallon bucket to bring the temperature down. And then slowly add this to the tank.
Doing some bad math... assuming a 100 gallon tank at 60f, 1 gallon of boiling water should raise the tank's temperature about 1.5 degrees. 3 gallons of 60f water in your bucket + 1 gallon of boiling water will be about 100f, the temperature of a warm bath. I shouldn't have to stress that it's a bad idea to pour boiling water directly into the tank.
That's 99 gallons at 60f + 1 gallon at 212f, average temperature of new water is 61.5 degrees?
In Celsius it's 99 gallons at 15c + 1 gallon at 100c = 100 gallons at 15.85c.
Not sure my math makes any sense or temperatures can even be averaged this way, but I wouldn't try this with a ratio larger than 1/100th of the volume at a time. And, still get some insulation on there ASAP... so your hard work isn't immediately wasted.
