Just a reminder that "cull" does not *necessarily* mean kill. It just means "remove from the flock".
As far as not killing them, until/unless the entire world becomes vegetarian, I'd far rather see people eat chickens (such as excess cockerels) that were raised well and happily at home, than buy factory-farmed chicken meat.
Assuming we're talking about culling in a breeding flock, here, to me "basic good health (including lack of significant defects such as crossed beak)" and "easygoing temperament" are the biggest priorities, followed by "body type correct for the breed", followed rather distantly by anything else like color or comb points or whatever. But everyone has their own goals and purposes, so one person's criteria may not be useful for another's.
(e.t.a - the one with the eye problem and the one that is not growing would seem the most obvious first priorities, unless the eye problem seems noncontagious and fixable and the bird has *very excellent* characteristincs otherwise. The old cock, 'sup to you how many to keep but certainly some people do remove the oldest ones from the flock)
Good luck, have fun,
Pat