I know what you mean - my old digital scales were great but the on/off button stopped working. My new scales I don't trust so much, especially for things that don't weigh a lot.
Saddled air cells can look scary but it's where the membrane has pulled away from the shell - it's not a massive...
The range is 12%-16% depending on the freshness of the eggs and I wouldn't stress too much. I use the average egg weight as well. I struggle to get mine to lose 12% with the humidity reading 25% in my incubator but I have great hatch rates.
Before I set them I work out the average weight and...