Don't worry, I'm clear that you're not criticizing the story itself.

It looks to me like you're trying to map this more strictly than is necessary for the story to still function as a critique. Omelas is not a capitalist society, but their prosperity is dependent on the unimaginable and cruel suffering of a child. That child is not a worker and cannot organize, but that child is still the very reason for their prosperity and decadence. So the people of Omelas have to maintain a dual consciousness wherein they recognize that their society is a good and beautiful thing but also that it is fueled by their collective abuse of this child.

This is about how we know capitalism doesn't work and causes unnecessary suffering but we're afraid to end it based on magical thinking. And there's a great deal of superstition in capitalism, in the stock market, in the invisible hand of the free market, in the cult of pain that surrounds it. You could perhaps believe that the bourgeois push these myths to be widely believed, but some of them evangelize to the degree where I think that if they are lying simply to fool us, they've additionally fooled themselves.

Liberating the child would absolutely be a violent conflict, one that would doubtless rend Omelas apart, and with good reason. Those who walk away are washing their hands of the entire affair (and perhaps are by the author not judged harshly, but again this is not something to hang every last moving part on) and personally I judge them for doing so. I think the author in general is letting us make our decisions about this society.