Part of the setup is that Prometheus believes you to be a one-boxer,

No. Nowhere does it say that. It only says:

Here was how he judged the blueprints: any that he guessed would grow into a person who would choose only Box B in this situation, he created. If he judged that the embryo would grow into a person who chose both boxes, he filed that blueprint away unused. Prometheus's predictive ability was not perfect, but it was very strong; he was the god, after all, of Foresight."

Not which was the case with me. Granted, Omega states that he created me, but I reject that you are allowed to draw conclusions from that, because among other things Omega telling a counterfactual me that Prometheus did not create me wrecks the setup so it can't possibly add up to sanity.