I thought I'd report back before closing this thread. My circuit works perfectly. I finally breadboarded it and it works as expected. It did require a few tweaks, however, including bumping up the first stage gain a bit, Av=3.9 instead of 3, dropping the second stage gain a little, from 2 to 1.85, and to crank both pots just a bit from their calculated values.
I tested the first stage alone, setting Vbat to 5.40V, and trimmed the offset pot (1.90V instead of 2.0V) until I got the desired output. All subsequent Vbat values followed perfectly once the gain was corrected (empirically derived). The second stage then tested fine once I dropped the gain and tweaked its offset pot (1.64V instead of 1.4V).
The drawing here is the final version with the gain changes. Also, the pots in the previous versions have been replaced by fixed resistors here, with their actual measured values.
Again, thanks for your participation! This was a good exercise for me.