I think you are answering your own question.
I am not completely comfy with the thought of doing it again tonight. My heart starts racing just thinking about it.
I would guess that if he is really interested in R, then he should be able to hear your reasons (#1-5) and accept them. Be open about how you are feeling about it, and revisit it again in the near future.
I am still in a deciding phase with my WS about what we are doing in the near future (R or S), but for now we are in the same bed. I am able to turn away in the bed and pretty much feel like we are in two separate beds. But I am also trying to get myself out of denial that we may be heading for S.
But you seem very clear about your needs. Communicate them.