You don't need insulation where you are. Having inside temps match outside temps is a good thing as it means you are getting the moisture out of the coop with the infiltration of fresh air.
You don't have to have 1 sq ft minimum of ventilation in the coop per bird. That is just a recommendation. The point is you need to target as much as you can without compromising draft free roosting area. If you have good air flow with a high volume exchange, you will have good ventilation.
I have T1-11 siding and just primed and painted the interior of my coop white.
You do look like you need more ventilation. I'd add more windows because I like lots of light coming in the coop.
What style roof is going on, how large of an overhang and what type of roofing material are you planning to use? I recommend a minimum of 1' overhang all the way around but prefer 2'. That enables you to leave the windows open wide without worry of rain blowing in the coop and offers baffling for strong winds coming it at the soffits.
Chickens are dusty creatures by nature and heavy coatings of dust are inevitable. I clean my coop once a year and it including hitting it with a leaf blower with the doors wide open then vacuuming with a shop vac to get a bit more before I add fresh bedding. I also have a hand broom with soft bristles and will occasionally swipe at the walls and shelves.