Don't know when you'll get this post, since it sounded like you were heading right back out again, but I agree with most of what you said. I may have come down hard on the plot since, for me, that's the easiest element to analyse.
But Mozart's music is, once more for me, too smart. I'm led everywhere, without room to manuever. The emotions I'm to feel, the insights I'm to have, all are arranged neatly for me and presented on a platter. I find it more satisfying to struggle with the music, insofar as my frailties in that arena will allow it.
'Per pieta' is the exception here; the sense of spiralling away from simplicity is physically disorienting as one listens. SFO's Fiordiligi went off-tone enough that I could hear it towards the end, which didn't help (recorded versus live is a conversation for another time), but I still found it astonishingly lovely and affecting, while much of the rest of the music was affected.
But you're absolutely right about the operatic outlook of the characters, and that the music is perfect for them. Unfortunately, on the surface the characters remind me of, well, the people in The Anniversary Party, with the exceptions of Fiordiligi and Ferrando. They both seem sincere, and I kept hoping through their duet that they would end up together. Alas, not to be, for the da Pontian gods of convenience decree that all must end wrapped tightly and bound with a neat bow of good humor. This may be regret of this contrivance that led me to ascribe emptiness to their moments together, which is certainly da Ponte's invention. Indeed, all of the characters are deeper in the music than anywhere else, something which is true of all Mozart's operas I've encountered. It may simply have been too much work for any librettist to keep up with this appalling gifted genius.
Great to hear from you! If you get a chance (and I know you're out nearly all the time, but still), send me any links you'd like for your section, and categories, etc. for them. Or just put them up yourself, I suppose.