It was a harsh winter in Michigan...and lots of other places too, places that aren't used to the cold and snow.
Ditto that adding heat is not a good idea....ventilation most important, good article link in my signature about that. I had frostbite when the temps hit nearer to 32 than the colder times because warmer air holds more moisture...temps would rise and so would humidity. Frostbite was mostly mild gray colored, had some larger black patches on rooster wattles...it all healed up with no infection using no treatments or preventatives.
Keeping water thawed and eggs collected can be time consuming. I have two plastic gallon waterers that I rotate...take the fresh one out and pick up the frozen/dirty one, one trip to coop, that worked well.
Mine didn't like to walk on the snow much either, kept part of the run shoveled and part is under coop so they did venture out when the weather wasn't raging.
A bit of straw thrown on top of the snow, and some scratch grain, can entice them to wander a bit more.
Space is always important, but especially for harsh winters when they might have to stay in the coop....Ridgerunner has an excellent article on space needs, link in my signature.