Let's look at the challenges you would face in achieving correct reading, rooting is not a magic key that let's you do everything easily:
The battery capacity (mAh) is coded in two places - the ROM and kernel (see Where are the battery capacity files located?) Only OEM would know from where the values are picked up, so you would need to have a custom ROM ...
If the battery is user replaceable, you can check the production number on that and try to decode battery date. I don't know if the manufacturer numbering scheme is standardised or if the app can be trusted to decipher, so I would suggest the alternative below.
Edit Accubattery Pro gives you an indication of estimated Vs actual capacity . I have no idea ...
This is most likely media related.
Devices on the network can be too chatty and try to constantly discover things and speak to each other non stop, keeping the wifi awake and active.
Two big culprits:
Spotify (uninstall or restrict all background activity?)
Google Home devices like the Mini (turn off "Let others control your cast media")
Also check out,