Your conclusion seems to be that the "repugnant conclusion" is not actually repugnant. That is, the "dystopian" world of a large population leading barely worthwhile lives is better than the original world of a smaller population leading fulfilled lives.

My impression of the repugnant conclusion was that it claimed that a large population leading barely worthwhile lives is, all other things being equal, always better than a smaller one leading much better lives, even if the worlds they exist in are otherwise identical. For this reason I thought that I had refuted the repugnant conclusion if I demonstrated that in two worlds with identical access to resources, the one with the smaller population with high average utility is optimal.

In other words I thought that the repugnant conclusion implied: Earthly Paradise<Galactic Paradise with trillions of people<Galactic Dystopia with quadrillions of people.

I thought that it was enough to refute the repugnant conclusion if I demonstrated: Earthly Paradise<Galactic Dystopia<Galactic Paradise.

No one is claiming that the galactic dystopia is optimal, given any quantity of resources.

The impression I got was that the Repugnant Conclusion claimed precisely that. I thought it claimed that it is always better to use resources to create another life barely worth living then it is to improve existing lives, as long as everyone else was already at the "barely worth living" level.

But you need to revise your ethical theory if, of those two choices, your ethical theory prefers the galactic dystopia, and your ethical intuitions disagree.

You may be right. The idea that the galactic dystopia is better than the Earthly paradise is still kind of repugnant. I may just have to accept that A+ is worse than A for some reason.