Thanks for this. Another important bit:
5,000mAh × 3.88V ÷ 1,000 ≈ 19.4Wh

I’m referring to streaming all audio from the phone over WiFi in the same way that Bluetooth audio can be streamed.

Cast is occasionally supported by specific apps, but there is no audio driver level support for any protocol.

DLNA / UPnP streaming is the most open and widely supported WiFi based audio protocol I’m aware of. Many modern stereo receivers can receive DLNA audio streams. Bluetooth has always had limitations both with range and quality.

Lower Wacker in Chicago is a black hole