I used the woman Jerusalem as an example because it is easier to see, and it shows that this style of writing exists in Scripture. If my example was just as contested as Adam, it wouldn’t help much. So, keeping in mind that I agree with you that it’s a metaphor, let me make my best case for a literal woman Jerusalem using arguments eerily similar to those raised for a literal man Adam.
First, the book of Ezekiel tells us when we’re going to get something figurative. Chapter 17 introduces a section with Yahweh telling the prophet to “propound a riddle, and speak an allegory.” Chapter 16 has no such markers. If the woman Jerusalem isn’t a literal woman, the text would tell us.
Second, if the woman Jerusalem was only figuratively a woman, Ezekiel wouldn’t give her genealogical information. Yet he tells us “your father was an Amorite and your mother a Hittite” and “your elder sister is Samaria” and “your younger sister … is Sodom.” Cities don’t have fathers, mothers and sisters. People do.
Third, there are other passages that speak metaphorically about Israel or Judah as God’s wife. Metaphorical uses don’t come from nowhere. If it wasn’t for God’s literal wife, Jerusalem, those metaphors would lose their foundation.**
Fourth, Jesus treats the woman Jerusalem as literal when he refers to her in Luke 13:34: “O Jerusalem, Jerusalem, the city that kills the prophets and stones those sent to her! How often I wanted to gather your children together, just as a hen gathers her brood under her wings, and you would not have it!” (Luke 13:34, NASB).
I’ve used the NASB because even though this translation, like many, adds the words “the city,” at least they have the decency to mark them in italics since they’re not present in the Greek. Jesus doesn’t call Jerusalem a city. He refers to her using feminine forms and speaks of her children. Cities don’t have children, but women do. It doesn’t work to see the children as a metaphor for the people who live in the city, since then it would be the children who killed the prophets, not the city they lived in. Cities, apart from the people within them, don’t stone people to death! Jesus speaks of the woman Jerusalem and her children as distinct entities, both personal.
That’s probably enough. My point is that all of the above misses the forest for the trees. Similarly, we could discuss all sorts of details about the Eden story and how it’s referenced in the New Testament, but none of that changes that adam means humanity, that Genesis records before and after the Eden story that the adam God created includes male and female, and that between those references we get a vivid story of the adam in a garden where two trees, a serpent and a human couple all seem to be more than they seem.
I’m not trying to convince you to abandon a sequential reading or an individual Adam (and I agree that a sequential reading is the best way to maintain an individual Adam). I jumped in because you mentioned not being able to see how anyone could reach “any other conclusion from the text.” Hopefully all the responses you’ve received make that a bit easier to see, even as you continue to see the best case pointing elsewhere.
** I know, this one’s really weak. It roughly parallels the argument that Scripture only speaks metaphorically of other people being dust, or all beasts receiving their breath from God’s Spirit because it literally happened to Adam in Eden. Not a strong argument in either context.