I believe you are most wrong about moral realism. I don't know exactly where you stand on every auxiliary issue, but:

(a) I don't think there are any good arguments for moral realism, and I think much of moral realism's appeal stems from misleading implications about the supposed practical consequences of antirealism. I think many of these misleading ways of framing antirealism are rhetorical in nature and rooted in biases and misunderstandings of antirealism, and that this is quite similar to how people critical of utilitarianism uniquely frame it as some kind of monstrous and absurd position.

(b) I don't think most nonphilosophers are moral realists or antirealists, and more generally I don't think moral realism enjoys any sort of presumption in its favor, e.g., I don't grant that it's "more intuitive" or that it does a better job of capturing how people are typically disposed to speak or think than antirealism (though I also don't think people are antirealists).

You ask what the most helpful or persuasive point I can make to start you down the right track may be. I don’t know for sure, since I am not super familiar with many of your background beliefs, but I’d start with this: I think there is little good reason to think that most nonphilosophers speak, think, or act like moral realists. Rather, I think moral realism is a position largely confined to academics and people influenced by academics. I think the questions about whether people are moral realists or not are empirical questions, and that the empirical data simply doesn’t support the notion that moral realism is a “commonsense” view. I don’t know where you stand on this issue, but I think it’s an important place to start.

I came to this conclusion after many years of specifically focusing on the psychology of metaethics and in particular the question of whether nonphilosophers are moral realists or not. Early studies suggested that most people would give realist responses to some questions about metaethics and antirealist responses to other questions. However, I came to question the methods used in these studies and launched a large project (which culminated in my dissertation) to evaluate how participants interpreted these questions. I came to the conclusion that most people were not interpreting them as researchers intended (and frequently didn’t interpret them as questions about metaethics at all). I suspect the best explanation for this is that ordinary people don’t have explicit stances or implicit commitments to metaethical theories, and that metaethics has very little to do with ordinary moral thought and language. The case for this is largely derived from my own data and my critiques and analyses of research on this topic. It’d be very difficult to summarize it but I could elaborate on specific points.

The more general takeaway is that I don’t think moral realism enjoys any special kind of intuitive priority, and I suspect that the reason why some people are disposed towards moral realism has more to do with path dependent idiosyncrasies in their particular cultural backgrounds and educations.