"Who does the Prophet speak to? Can we agree that he is speaking to TWO groups of people simultaneously, in the same sentence?"
Hey, I think I already said that! :-)
The passage in Genesis is certainly an example of that -- God is simultaneously speaking of both Eve and of the Theotokos in the one verse.
I was doing some reading about the book of Revelation, which the Orthodox Church treats in a way that is unique within its treatment of Scripture. The Wikpedia article had a short passage about the Eastern Orthodox view of that book that nicely encapsulated it and Orthodox readings of prophecies in general, pointing out that it didn't fit into any of the traditional interpretations that were mentioned earlier in the piece:
"Eastern Orthodoxy has an interpretation that does not fit well into any of the above classifications. It treats the text as simultaneously describing contemporaneous events and as prophecy of events to come, for which the contemporaneous events were a form of foreshadow."
That's the other excellent example in Scripture about multiple uses for the same verses. Such as Rev 12 and the "woman" (the same from Genesis 3:15!), who represents Israel, the Church, and Mary. I think Catholics would agree with the Orthodox's interpretations of the book of Revelation.
Regards