I didn't read all of the posts on this thread- just saw you mentioned the float test. I just thought I'd add here, we did the float test for 10 eggs in our incubator who hadn't hatched by day 25. The float test said about 7 of them definitely should have been viable... we opened the eggs in a last desperate attempt to help. They were all dead- the float test did not work for us.
I hate the float test! Well, correction, it's good for eggs you want to eat, to determine if they are fresh or old.
But it's not good for incubated eggs. It definitely cannot tell you that a chick is dead. No way. Sinkers are not always dead. Floaters are not always alive. It *can* let you know one is alive, if it moves, but if it doesn't move, that does not mean its absolutely dead. And if the chick is alive, a good candling should reveal it anyway, making float test irrelevant.



