I dont know if 1 rat per month is enough or not. I do think it's a mistake to underfeed based on the ir feeding habits in the wild. A wild snake is responsible for it's own welfare. You are responsible for the welfare of your snakes. Nature is cruel. Why would we want to replicate that cruelty?
In the wild snakes die. They starve, they get eaten, they freeze to death, and meet their demise in a variety of other ways. Few animals in nature die of old age. Is this what we want for our snakes? Even humans before agriculture ate what they could get, when they could get it. Many starved, and the life expectancy was half what it is now. Should we go back to that because it's natural?
1 adult bull snake: "Dozer"; 1.1 juvenile bull snakes: Oscar and Phoebe; 3 baby red-sided garters; 1.1 macklot's pythons