Put a 16V battery in it and go buy a 2000watt Predator brand inverter from Harbor Freight. It's only $449 and the guy there says same people make them that make the Hondas. Don't know if that's true, but I have one and it has been great. VERY quiet, like a Honda and uses little fuel. I would think you need a generator anyway to keep a pad on the pan for some heat. I know I wouldn't be firing my engine in temps that cold with the oil and water that cold as well

As far as your battery, if it is pulling that much now, it likely has no chance of cranking the car in cold weather