they do eat their own eggs. Sometimes it can get to be a problem. but I haven't had this problem get to the point where it bothers me. Sometimes I feed the chickens raw egg willingly. They suck it up. There is human food a chicken simply refuses to eat.
I am not sold on the "once and egg eater always" theory, I have had some young ones do it in the past and they seemed to have gotten over it but, this is yet another young flock and it been going on for a little bit longer than I like and a cant really catch who it is (37 hens in the house) and it is not a lot, just oneor two here or there, I have just been pulling the beat 'em to it method.........
Nest boxes need to be at least 18 inches above the floor of your coop, and lower than the roosts. The boxes also need to be fairly dark inside, maybe covered by a curtain. If the hens can't see the eggs they are not tempted to peck them. Gathering the eggs often might also help.
THe boxes are up off the ground and right now i am gathering several times a day......I will try the other things you mentioned. Also i was told that the Flock Block at tractor supply helps a ton.....so i will try that too.