Nope, it's confusingly phrased, but my reading is the last "er" in the crucial sentence refers to Friedrrich Christian, not August III.

Okay, thank you! I wasn't sure if you could actually have "er" switch referent in the same sentence like that--usually German authors I read go out of their way to not do that because it's confusing! (This translator confused me a number of times with pronouns, I think it's a feature of him specifically.)

But "meine Alte"/"mein Alter" was much later used between married couples as well, though in that case the association would be lower class streetwise couples.

Interesting!