Can it be used while charging?

Several people have reported different results so I experimented. I find that the Anker SoundCore mini will not play from AUX while recharging from a USB data host such as a PC (whether or not the host is trying to use it as a USB client). However, if I try to charge the Anker SoundCore mini from a non-data USB charging source, then it will play sound over AUX with a loud static hiss. It's probably a ground loop being amplified. I installed a small inexpensive "ground loop isolator" which you can also find on Amazon and this cleared the problem entirely. (https://www.amazon.com/AUKEY-Ground-Isolator-Systems-Included/dp/B01L1NP7YI/)

how do you know which FM station you're tuned to -- any kind of readout?

There is no way to see/verify which station you're on. It makes tuning the radio a little bit challenging. I've actually used this speaker a lot for the radio function, but I keep it on the same station all the time. A couple of times I accidentally held the volume button too long and changed the station. When you do tune it, you need to hold the up or down button for a few seconds and wait till you hear the new station playing. If that is not the station you want, continue the same process. I find that I need to give the tuner a few seconds on the new station before I attempt the press and hold again to change the station. It's a little finicky to say the least. But, the sound is great considering its size and I love how little space it takes up! You'll get the hang of it, so don't let that deter you from buying this little speaker.

when scanning for FM stations, how do you get it stop on the channel you want? If I press the play button it goes back to the first station it was on.

Holding down the play button will scan for radio stations. Let it finish scanning and it will stop at first saved station. Press and hold volume button up to select next saved station. The stations are saved automatically. Hope I helped.

Does it really have a 66 ft bluetooth range?

The range depends on a lot of factors. Things such as: line of site (walls or any furniture in the way); other bluetooth devices; the strength of any nearby wifi (the frequencies are very close); etc. will effect the distance it will work. If you go out to a field, with no other devices anywhere nearby, and a clear line of sight, you might get 66 ft out of it. However, for most of us, you'll never get it to work over that distance.