The surest way to check the humidity is to candle and weigh the eggs frequently to check the size of the air cell. Weighing the egg and adjusting the humidity level to keep the weight perfect is probably beyond most of us, but there's info on how to do it at
http://www.brinsea.com/customerservice/humidity.html if you're game. Susanne's candling article at
http://www.internationalcockatielresour ... -eggs.html has some info on proper air cell size toward the bottom.
It seems to me that all males have a white halo on the edge of the cheek spot, and I get the impression that Susanne really considers it to be a sign when it's pretty big (as Bio's is). But last time I looked in, the people on that other forum had the notion that any white halo at all is a sign of a split.
I'm doubtful about the signs myself. Ladybug has streaking in her cheek spot which is supposed to be a sign, but so far she has produced zero WF babies with a WF mate. But so far she has only had four babies where I knew for sure who the daddy was, so I haven't completely given up on the split yet.