On candling, I know it's weird, but I only candle on about day 18 and toss the ones I know will not hatch. I have had good results doing it this way, but understand the desire to know how many are developing before then. I only need to make room in the hatcher for the chicks to roll around once they are out. If I can't tell for sure that there is a wiggling chick in there, I leave it as long as it passes the sniff test.