Question 1 answered:
Good news is that 8 hours later the phone's OLED screen is still burning brightly, so apparently it is getting power through the USB cable, nevermind the lack of a charging indicator light.
Bad news is that I'm still in the Fastboot screen.
4. Is there any way that I can get the computer to recognize an already Fastbooting phone, that is apparently unresponsive and thus unrecognizable?
Or do I have to just deal with the phone by itself, which gets us back to Question 3 above?
And returning to Question 2, is there any harm in pulling the battery, or am I at the point where that is a sure-fire bricking?