To return to G-d from their sins via teshuva? Yoma 86b

Question

In a previous post the question is asked how Hashem could remarry Yisrael if in Devarim (24:4) it is written that it is assur to remarry a divorcee after she strayed with another husband?

then her former husband, who sent her away, may not take her again to be his wife, after she is defiled; for that is abomination before the L-rd: and thou shalt not cause the land to be sinful, which the L-rd thy G-d gives thee for an inheritance.

To this, Sifrei Devarim 306:2 is quoted saying:

Afterwards Israel is destined to say: But You have already written (Jeremiah 3:1) "If a man divorces his wife and she leaves him and marries another man, can he return to her again?" He: Did I not write "a man"? And have I not already told you (Hoshea 11:9) "for I am G-d, and not a man!" And have I divorced you, house of Israel? Is it not already written (Isaiah 50:1) "Where is your mother's bill of divorce by which I sent her away, or to which of My creditors have I sold you!"

On this, I have the following question:

1. The Gemara (Yoma 86b; sefaria-edtion) states: "it should be prohibited for the Jewish people to return to God from their sins, yet repentance overrides this prohibition" - What is the foundation of this statement? How can Rabbi Yochanan have said this? As said by the OP of this question, this would be "adding to mitzvos", right?

The answer, and specifically the comments under that answer aren't really answering my questions, hence I'm writing this question.

Answer 1

This is beautifully poetic, the halachot of adultery are not exactly copy/paste to Avodah Zara, but this is still Emet and stunning (and yes, following Steinzalz, Rabbi Yochanan is referring to the halachot of adultery). Even if we were to take it very seriously in a halachic context, the simplest answer to this question is why do you need to assume this is "adding" or "removing" from the Torah? If the Torah itself says it, then that's not an addition or a subtraction. It is a clarification of the circumstances of the application of the halacha.

The Zohar states: ישראל ואורייתא וקודשא בריך הוא חד הוא

In Yevamot 102b we have the following (Koren commentary between the lines):

Parenthetical to this discussion, the Gemara relates: A certain heretic said to Rabban Gamliel: You, the children of Israel, are a nation whose Master removed [ḥalatz] Himself from them, for God has left you in much the same way in which a yavam would perform ḥalitza with his yevama, as it is written: “With their flocks and with their herds they shall go to seek the Lord, but they shall not find Him. He has removed [ḥalatz] Himself from them [meihem]” (Hoshea 5:6). The heretic tried to use this verse as scriptural support that God has performed ḥalitza with the Jewish people.

He, Rabban Gamliel, said to him: Imbecile, does it say: He performed ḥalitza to them [lahem]? Rather, it says “ḥalatz from them [meihem],” meaning it is as if they, the Jewish people, performed ḥalitza on Him. But if a yevama had her shoe removed by her yevamin, does this have any significance? Here too, the meaning of the verse is that the nation of Israel abandoned God by removing themselves from Him, and this abandonment has no significance.

There can be no separation, ultimately, between the Jewish people and Hashem. The "it should be prohibited"