oh no. You're in my climate.
First your chickens will probably pick one coop, especially cause you have a rooster. They will all wanna sleep with the roo and he may even harass them if they don't sleep with him. Just my experience.
Second unless you have a roof on your run you will have days that not a single chicken will leave the coop. You can house maybe 6 chickens in the big coop. Not because of ventilation but because chickens need room to live. If a chicken can't leave its coop, it needs room to flap its wings, stretch its legs, get away from the chicken it doesn't like, etc. 4sqft isn't a lot to do that in and that's what most people consider acceptable. Your "big" coop would be good enough to provide that for maybe 6 birds, but would be better for four. You cannot keep 8+ chickens like that and expect them to be healthy or happy. It's not so bad now while the days are long and the weather mild, but once the lake effect hits they will rip each others feathers out and peck combs til they bleed or bully one another out into the snow.
And yes, your husband is wrong about the lots of birds makes for warmer chickens. Good ventilation , solid winter bedding management, and proper stocking to space ratios makes for warm chickens.
Good news is if you need to rehome the birds the local Craigslist community is active and will frequently snatch them up if you price competitively.