Yes, it really is that bad. We have a resin printer at work and it has been banished to a different room due to the resin fumes. The table it sits on is perpetually sticky, and we go through twice as much IPA postprocessing the prints than we use in resin
I mean, you can grind your own mirrors, how hard could it be? (Spoiler: very hard)
Near the bolt holes joining the two halves, you can see thin strips going across that overhang gap. Those eliminate local sagging without needing support material. The part could have been flipped 180 instead, but then the outer edge rim would be unsupported.
Not directly answering your question, but if you haven’t already you should take a look at the end of life disaster recovery repo.