Hi. Welcome from Central Maine. Your set up is very "doable". Suggestions, some of which you may already have in place or be contemplating:
1. Keep ventilation open all winter. Just be sure the wind/breeze can't blow on the birds as they roost. Only close down as common sense dictates during a blizzard with blowing snow, or sub zero temps. Recommended ventilation is 1 s.f. per bird.
2. Be sure the perch is far enough away from back wall and ceiling so that they don't touch it with their feathers. Ideally, the perch should be at least 2' below ceiling, 18" from back wall, with enough space in front of it so they can fly down without doing a face plant on the wall in front of them. If that's not possible, then give them a ramp to the perch.
3. Predator proof: If you can push a quarter through any opening, a weasel can enter. A single weasel will kill an entire flock in a single night just for giggles.
4. Deep bedding: Added insulation. If you can put a plastic barrier to protect the wood floor, then put down a deep bedding in the coop, that will help them to retain heat. I use leaves, grass clippings and other compostable materials in my coop, with the bedding usually 12" deep under the perches. I clean it out 2 - 3 x/year.
Deep litter in your run: Shovel all of that removed bedding from the coop straight into the run. Natural materials compost much easier than shavings. I only buy shavings when I run out of stock piled leaves! Deep litter provides all sorts of benefits: attracts beneficial bacteria, fungi, insects, worms to help keep pathogens in check. Birds who have access to deep litter have healthier flora in their guts, improved immunity, improved viability, improved feed conversion rates, decreased issues with disease. Soil covered with deep litter is much healthier than bare fecal impacted soil which is seen in many chicken runs.
5. Sun room: Cover all but the south side of your run with plastic. If you can, create a peaked roof over at least part of the run to shed the snow. I use a green house tarp over a truss system that sits on top of an old swing set. Mickey mouse, for sure, but it does a nice job, and creates a nice space for the flock to shuffle through the leaves all day long, even with cold blustery winter winds! I have to knock the snow down often, sometimes 2 - 3 x per storm, and yes, even in the middle of the night. But, IMO, it's well worth it.
6. Come visit us on the Maine thread!