I appreciate the effort and also the argument you just made here supports a crypto-prescriptivist position, ie, normative speech is a rortian word game to be won with appeals to morality, since
Commands are rhetorically stronger when they can be attributed to a common belief in a higher thing, and not our personal preferences.
ie, your correct points about how the language no longer makes sense when you make prescriptivism (or emotivism) open and explicit also explains why people don't make statements that way.
All of your examples carry more sociopolitical force when they're reframed as claims about morality. Which is, of course, why people do this *at least* as often when doing dirt as when they are acting righteously.
Commands (downstream of preferences and other feelings) obviously work better this way, because they permit us to dodge attribution for the imposition.
Of course that doesn't imply moral realism is false (and I hold that it isn't) but it is a weak argument. I think a stronger argument would have to back away from linguistic sense --not what 'makes sense' to our verbal processing faculties (we know to be largely cope), but rather grounded in better measurements than "but then it wouldn't parse".