Re: connection between air in the return and CYA consumption
No autofill but we have had a fair amount of rain this year. Although I've only had to drain about 1" out so far all summer, and add about 1" during a dry spell. Started monitoring this about 2 years ago, and compare it with the CH level, which drops slightly over time (fill water has a CH of 50), but not as much as the CYA. I used to think it was splash out. When the kids where younger they would create waves with the big tubes and send water flying out of the pool.
I have noticed if I leave the bubble cover on during a hot sunny day, when the pump turns off, the water near the surface can get pretty warm, like 94-95. Maybe that accelerates the loss? I haven't kept records on the CH/CYA loss, but I do need to add ~10ppm CYA per month throughout the season.