I'm afraid I don't have all the answers here but I think if you check your manual it should mention something about operating temperatures. I've had my Canon Rebel XSi out in -10C and -20C for a few hours here and there but I never left it out 24/7 so I'm not sure if that would make a difference.

You are right to be concerned about condensation in the tent. If you want to bring it inside then you should get a plastic bag (like a big Ziplock bag) and put the camera in the bag and seal it before entering the tent. This will let it warm up without getting covered in condensation.

Maybe someone else will have better advice.