Every time I have had problems with pecking/pulling feathers, it has been the older hens doing it. Once I got rid of them the problem was solved. Which was fine for me because they were usually around 3 years old and had slowed down on egg production. Have found the same solution to eating/pecking/breaking eggs. It's always the older hens, in my experience, and when I cull the older hens the problem vanishes.
Ugh. So not what I wanted to hear, but I agree, the problems are only with the older hens. That sucks. I am too attached to mine to kill any of them. I'll just continue to keep her in a separate coop with the rooster. They seem happy together.