My first time using Dr. Prius - are these numbers good?

(I originally posted this on the Prius V forum, but then realized that for engine/battery stuff in a Prius V I should post on this forum instead)

I'm trying to learn more about the hybrid battery system and eventually become a Prius wizard.

Currently driving a 2014 Prius V with close to 80k miles on it. Car currently runs fine, and an OBDII scanner shows zero error codes, but I think the hybrid battery has gotten significantly worse since buying it at 70k miles last year. "EV mode" seems to last for less distance every time I try it, and EV mode will end (engine restarts) at much lower speeds than it used to. Also my gas mileage is slowly getting worse - average dropped from about 40 to about 37. All this makes me suspect that the hybrid battery is dying.

I downloaded Dr. Prius and ran a battery monitor log (spreadsheet attached) while idling the car. I kept an eye on the "VOLT DIFF" statistic while doing it - VOLT DIFF is not reported on the spreadsheet but it hovered around 0.04-0.08V while the car was idling. Is that bad? I've heard it should always be zero on a healthy battery.

Is there anything else I should be looking for in these test logs? Do I need to buy the full version of Dr. Prius and do a full battery test to learn if my battery is going bad?