Well, it's always possible that I have dropped a name or two here or there. But whether I did or not, I'd concentrate more on the fact that since I've pretty much dismantled the Euthyphro Dilemma in the past, whether anyone realizes I did or not, I'd say that it really should no longer be seen as having any place at all in the skeptical apparatus of evaluation which skeptics try to use to knock the monotheistic God of the Bible off of the table. With that said, I'm at pains to see how there's much left for you or any other skeptic here to hoot about in your OP. (And yes, I'm FULLY cognizant and aware of just how jarringly audacious, maybe even narcissistic this sounds of me to say it....in just this way. But, there it is!)
On the other hand, I will give you this much, though,--- and the credit I give to you here, NV, doesn't come from any further wild gesticulations that could be made over anything Socrates might have said through Plato, --- but it rather comes from the nature of basic theology in the Bible, and it is this: if God's 'fuller moral truth' comes only by Specific Revelation and not so much by General Revelation, then you have a partial point that Christian Morality isn't objective but rather Subjective.
Moreover, your skeptical contentions here may very well reflect some of the Kierkegaardian notion about how our own individual positions of Subjectivity (by which I mean his definition of the 'Subjective' and not the usual run of the mill definition of the same term) can only partly engage with Objective attempts to marshal systemically ethical insights about the moral Reality in which we all live (or in which we think we live).