when you say you did a float test, what did you see?
You aren't looking for if they will float, all the eggs will float- you are looking for movement. I would take each egg and candle with a phone torch, candle from the air cell, hold the egg still, look for veins, look for movement. If you can, photo each egg while being candled and post here.
With the homemade incubator, if it is still air (without a fan) the temp should be 101-102 degrees F, so yours have been a little cool and may be developing slower if they are alive.