Aside: Just so I personally don't get lost in our current discussion, I am reminding myself that this is where we started, with Mike's post on FB:
"Mental pleasure exists only when you have peace of mind. Peace of mind exists only when you have no more fears and worries. Fears and worries exist only if you are still wanting. You are still wanting only when you have no limit in what you want."
I am still not sure that the "physical" question of whether we can experience pain and pleasure in different parts of our body at once is really the issue, although that will be interesting to continue discussing and possibly answer.
The original question was more like: "whether the uses of "only" in this set of propositions are an accurate restatement of Epicurean views" which I don't think is necessarily the same issue.
And I continue to think to myself that we need to keep in mind that (in my opinion) this entire issue came up first in context of a LOGICAL argument (the refutation of Plato's arguments in Philebus) rather than a "medical" or a "clinical" context. I suspect that is highly relevant to this discussion because I think the main focus is really on the logical point that nature gives us no faculty of choice other than pleasure or pain, very broadly considered as "feeling." And that would mean that the primary issue Epicurus was addressing was probably "feeling vs reason" or "feeing vs religion" and not "whether pleasure in toes can simultaneously exist with pain in fingers." Because if a third guide exists that would tell us how to regulate choices between pleasure and pain, then that guide would be more important than pleasure and would deserve the title "guide of life." In Epicurean terms reason and logic and wisdom and virtue and the rest cannot meet that test, because they are still simply tools for the attainment of the feeling of pleasure, so pleasure always remains in primary seat.
So I doubt Epicurus was concerned with the question of whether he was multi-threaded or single threaded in experiencing intense physical pain alongside intense mental pleasure on the last day of his life. He might say to us that whether he was experiencing them simultaneously, or flipping back and forth between them as his attention refocused, would not be important to the discussion. He might say that the only thing important to the discussion was that FEELING (not "reason" or religion or the rest) remained his guide to the last moment.