On the topic of ventilation, there are several concurrent threads running on the Woods coops, which were designed to maximize ventilation. These were designed over 100 years ago and one of the issues cited by Woods in his book, and the reason for his design, was all the frostbite seen with birds in closed up coops in winter. Without ventilation, moisture builds up (source is from the birds themselves.........mostly from their breath) and the moisture is what causes the frostbite issue. His claims then, and it seems to hold now, is birds in his well ventilated houses will come through fine, whereas birds in closed up houses.....nearly adjacent to his, will suffer frostbite. That is pretty much the issue in a nutshell.
So if you want to duplicate the process, you need to open up the coop to let the moisture escape and get good air turnover. How you do that will depend a great deal on how your coop is setup.......some designs lend themselves to it, and others will be hopeless deathtraps if opening the coop up results in a drafty house (read wind chill) or creates openings for predators to enter.
Birds will survive OK at those temps (and lower), but only when conditions are right. If you are getting frostbite and can't do anything about venting the moisture that is causing it,, for the short run, you may want to consider some type of supplemental heat, knowing that too has it's risks. For the short term, be thinking "keep my birds alive", and nothing else related to motivation or anything else needs to be considered. Get through this, learn from it and plan to do better in the future.
BTW, I have my water bucket inside my Woods coop, right at the front. It has both a cup and horizontal nipple, and is kept from freezing by using a submersible bird bath heater in the bucket. Neither the cup or the nipple leak, so water is not an issue. I can leave my birds in for days on end if need be and they will always have food and water.