Looks like you did your homework and made some well informed decisions. Thanks for sharing the details of your story and the pictures! (I, too, have a white base model, 2018).
We bought ours used, taking a bit of a flyer on it, since we did not know nearly as much as you did about the Clarity. We love it. And find this forum useful for sharing car behavioral info.
One surprise: we expected that in buying a 2018 PHEV that the pace of automobile technological innovation would mean that by now we would see many cars with performance (and price) that would make our 2018 Clarity seem obsolete, or not that competitive. Wrong. The car is almost 4 years old and there isn't anything comparable on the market that has this price/performance combination. Yours will be a lucky son to inherit this unique car.