I used your 75" and assumed that the coop is square. If one multiplies 75 by 4 for all the walls and then multiplies that by 1.5 you will get 3.125 square feet of ventilation.
The rule of thumb for ventilation is 1 square feet per bird, 24/7 but most important when they roost. Your roost will accommodate 6 birds, your coop will accommodate 9-10 although the run would be too smal for that number. I see you have four birds.
I suggest that you consider adding additional ventilation.
"[Kansas] has plenty of raccoons, armadillos, skunks, badgers, minks, foxes, rabbits, hares, snakes, and bats." Mink are able to get through a 1" square opening and generally can evade dogs.