You can eat any chicken regardless of sex and age. The secret is to cook them slow and moist. You can look up that comfort food called chicken and dumplings or use the French standby Coq au Vin, literally cock and wine which is a traditional way to cook an old rooster but would work really well on old hens. I often use a crock pot. Some people use a pressure cooker too, which does not use slow but the pressure and moisture works well.
There are different ways in how to keep a flock young enough to lay well. Some people just replace the entire flock when egg production slows. I use a rotation where a hen never gets three years old.
My normal laying/breeding flock is eight hens and a rooster. Every year I keep four new pullets. Those often lay pretty well over the winter without me adding additional lights. I keep the previous year’s four hens over winter, letting them go through the molt and recharge their system. But when the previous year’s four start to molt in the fall, I eat them. That way I only pay to feed four non-producing hens through the winter and get the benefit of the larger eggs they lay after a molt.
So in the late summer/early fall I may have eight hens and four pullets laying but I only carry 4 hens and 4 pullets through the winter.
Egghead, my feed is a little more expensive than yours, closer to $17 for 50 pounds.