I haven't read the whole thread yet, but have you thought about using a Wool Hen? I've raised lots of biddies without using any electricity in the winter (20s at night) by using a Wool Momma. If they get cold, they will move further back into the tunnel, if they get warm, they will move towards the front opening. And you don't have to worry about fires, or the electricity going out.

They also don't have the eye and mental problems associated with using heat lamps. They seem to develop more natural circadian rhythms without lights.