Sorry, I can't give feedback on Levels work here, only in the Levels Class.
However, I urge you to revisit your notes from the class, regarding the order in which you'd approach small areas like his head.
Hi Sarah, I've moved this post into AD, since it's not a class question per se.
This is very interesting. It's actually rather common, but usually the difference in print size is bigger than this. Usually 4x6s and 8x10s would be printed on the same machine at the lab. However, it seems like that might not be the case? If they were printed on different machines, and one of the machines was running a bit dodgy that day, it would be the most common explanation for this.
Have you asked the lab about it?
I urge you to run a cleanup program once a month. However, in general terms, all of those specs sound fine.
Do you happen to know if the error message arises when you calibrate the laptop screen? Or is it only the external?
No, once that jpeg damage is done, it's done. You have to start again from the raw image.
PLEASE read: https://www.damiensymonds.net/2010/02/trash-those-jpegs.html