Check out the new interface for the Aa menu for 5.12.3. If you don’t like it, just manually download older firmware versions.
Mind, there was also a change to the Aa in 5.10.x. It added support for preset and customizable profiles but that also added an extra step if you want to manually adjust font sizes.
Any of these should show battery percentage. Personally, with how long battery life is on Kindles, I just found the percentage annoying and gave me unnecessary battery anxiety.
https://s3.amazonaws.com/firmwaredow...e_5.10.1.1.bin
https://s3.amazonaws.com/firmwaredow...ite_5.10.3.bin
https://s3.amazonaws.com/firmwaredow...ite_5.11.2.bin