Had a second, much nicer talk with Mr. DB.
Asked more questions and proposed a few scenarios for future reference/so this doesn't happen again.

Questioned him about the year delay which weirded me out, he said it was a deliberate Covid relief directive to
not chase people, but since January 1st over 2000 letters just like mine have been sent.

My earlier assumption was incorrect.....
Bill of sale from an individual or any non-dealership is meaningless to the state.

If I ever embark on something like that again, turns out the best protection is get an appraisal
and/or take it to a dealership and get a "what would you give me for it today, as it sits" price,
before doing any work. Mr. DB says they would seriously consider that. So, that's the future plan
if I go this route again.

It's one thing to waste my own time running around getting estimates for stuff I don't really intend to do, to meet retail value....
(I repaired the important stuff), but I can't jump into a time machine and get an appraisal from the past, and I'd feel bad wasting
the time of the businesses I would be visiting to pile up the estimates. Rather not and won't.

So I will just pay the stupid thing and chalk it up to lesson learned.

If I do it again, will get an appraisal to cover my posterior.