The section where the Creator is telling her to return is regarding future prophecy. It's something that is mentioned over and over - including by the prophet Hosea - who confirms the lost sheep of Israel are indeed the gentiles of today. He says we will go many days without a king. But there will be a return. This prophecy is mentioned as early as Deut 30:1.
This is really all over the place. Gentiles were never God's "chosen people" (Israel literally meaning chosen). They were not a divorced wife because they were never illustrated as being God's wife in the first place. But then, throughout Romans, Paul does indeed describe that "chosen" means something different spiritually, like when he says "not all Israel are Israel," referring to how some fleshly Israel weren't spiritual because of unbelief, but by no means does this have anything to do with some concept of divorce/reconciliation situation with Gentiles. This is a massive confusing of concepts.
And besides, once again, you've continuously made a distinction between people's who have been divorced vs those who haven't, and that would imply that your quote of Romans 7 ONLY applies to the ones divorced with a certificate and all, hence not everyone actually needs Christ.
The verses after verse 8, in which God issues the certificate, refer to a comparison of Judah and Israel, saying that Judah was WORSE. Verse 9 says "so it came to pass," and therefore we have a concept of an actual
sequence in Jeremiah 3. We started with Israel's backsliding, then the divorce, then "so it came to pass" that Judah then -- in sequence -- proved even worse than Israel, but then:
11 Then the Lord said to me, “Backsliding Israel has shown herself more righteous than treacherous Judah. 12 Go and proclaim these words toward the north, and say:
‘Return, backsliding Israel,’ says the Lord;
‘I will not cause My anger to fall on you.
For I am merciful,’ says the Lord;
‘I will not remain angry forever.
13 Only acknowledge your iniquity,
That you have transgressed against the Lord your God,
And have scattered your charms
To alien deities under every green tree,
And you have not obeyed My voice,’ says the Lord.
As a sidenote, if Judah was worse than Israel, then why would Israel get the certificate (point of no return) but not Judah if the matter was so significant as you make it out to be?
All of the statements segue as a sequence, hence Israel was beckoned to return after -- and only after -- she acknowledged her iniquities, hence the adulterous woman returns to her husband ONLY if her relationship to another man is renounced. It's the same concept throughout Scripture: repent first, then join to God.
There's one more simple issue that I think isn't being addressed: you and some others are imagining that the law of Deuteronomy 24:1-4 takes effect merely after the divorce, in which case that the law would simply end with the sending away with the certificate meaning the first husband can't take her back, but it doesn't. The "defilement" of the woman, being the current condition of the woman, occurs after the second marriage in the scenario, and then, only at that point "after she is defiled" -- not just upon/because of the certificate -- is the first husband forbidden to return.
It's the pervasive concept of Old Testament vs new, repent with water and THEN the infilling with fire: remove oneself from the joining of idols, then join to the true God. We cannot have both. The whorish joining must be renounced and then a rejoining -- or a joining in the first place like we see with Gentiles as a group and a symbol -- can occur.