I agree with much of this.
No, yes and yes. The $600 reporting threshold for the 1099-K is new in this context - it used to be $20k and more than 200 transactions a year. The IRS did postpone the new $600 requirement with respect to 2022, but you are right that it doesn't mean they can't send a 1099-K - which appears to have been the case for the OP.
Correct. So not doing anything for this sale would not IMHO be wise.
You could also start with TurboTax (or a similar program). I've already filed my taxes, but I went back into the program pretending that I was amending the return to add two Forms 1099-K. The questions are pretty straight forward, but I did need to use the "search" function for directions on where to put in the basis.
I entered two fake 1099-K entries - both for large numbers, and chose "Personal item sales" for each after entering the dollar amounts. One one I chose "All items were sold for a loss or no gain" and that 1099-K seems to have been ignored for the rest of the tax calculation (I didn't dig into schedules). The other I answered "I sold some items at a loss or had no gain" and then had to manually go find another page and enter in the amount I paid for the items, dates acquired and sold, and since I showed I paid almost nothing for the items, my income and tax bill did go up.