I think the implication was Abraham's resurrection. Jesus was an apocalyptic Jew after all.
Other than that, your reasoning seems fair, but we don't know what was going through the head of the one who wrote those verses. Something convoluted, for sure.
I'll hold off on that till Catholics comment on it. Had to be?
I was raised Eastern Orthodox. I have as much to say about it as any Latin. They recite it every now and then; the Orthodox recite the Creed every Sunday.
Right then. If the Third Person of the Godhead was speaking at Ex. 3:14 then so too at vss. 15, 16 etc. because there is no change of person speaking.
“The Creed leaves no doubt that it had to be the Holy Spirit (”he spoke through the Prophets”).”
The Spirit is YHWH God of Abraham, Isaac and Jacob according to the Creed? Where does that leave God the Father?
“I think the implication was Abraham's resurrection. Jesus was an apocalyptic Jew after all.”
I won't make that leap. The discussion of Jesus’ age, etc leads me to believe that Jesus is saying pretty much what it appears he is, that he existed before Abraham.
For certain if understanding the meaning of what someone wrote is difficult I'm not going to attempt a manuscript mind-meld.