I know this piece ... in that I have heard it before, not played it myself. Yevgeny Sudbin plays it on his Scarlatti album
(track 11). In the notes he says only that it "lacks a K number since it does not appear in Kirkpatrick's catalogues" and that he hears in it "the bitter wail of a gypsy lament". It is not one of Kirkpatrick's 555; I should hesitate to say that it couldn't be by Scarlatti. His style is very diverse and I don't think this piece in particular is so alien to it as to rule it out.
As for your playing, Richard, I thought it was very good. I agree that it could perhaps be a touch faster and the ornaments a bit less indulgent. I tend to think of "largo" as more a matter of approach than of speed per se, if you see what I mean (much as my wife is fond of saying "allegro is a state of mind"
). Re the dynamics, we could argue about this until the cows come home, and probably will. I again tend to the pragmatic side; a piano is not a harpsichord and if you're going to play Baroque music on a piano you might as well make use of some of the advantages (and acknowledge the disadvantages, as David says re ornaments), as long as you don't try to play everybody as if they were Chopin! Terraced dynamics are discrete dynamic levels for a phrase or section ... think pulling out or pushing in a stop, so the transition between them is stepwise. No power in the 'verse can stop a pianist applying a bit of phrasing within a section, of course, but big crescendi and decrescendi to go between sections are out. You could make the contrast between repeated phrases a bit clearer. But I think you should have no reason to be afraid on submitting a recording like this. (Anyway, shouldn't that be "salutamus"?)