Nice setup you have there. I think it will work great for you. I had a similar setup (with a bucket) down to -9F last winter.
The only comment I would make is it doesn't look like your heated waterer is secured in any way. You have that board to keep them from roosting, but they could *possibly* come in from either said and hit it (one chicken being chased by another, ie), knock it over and perhaps have a hanging heater loose in the air or possibly on the ground. The cage you built around it seems like a very good idea to reduce the chance of fire in such a case. And the heater is supposed to have an auto shut off feature but that could fail. I know...all a worse case scenario and unlikely to happen. But a little securing wouldn't hurt nonetheless. Perhaps even a small loop of rope that would attach to an eye-loop on the anti-roosting-board with a spring latch.
I did have our birds knock over our 5 gallon horizontal nipple watering bucket this summer, multiple times. This only happened when the bucket started to get low in water and was probably due to them perching on top. Now that I've got the heater installed in the bucket, I've secured the handle with an adjustable cargo strap to the ceiling, which both secures it from being knocked off the cinder block and doubles as a roosting deterrent.
