The 70 nations and Matan Torah

I am sure most people are familiar with the ma'amar chazal that HKBH offered the Torah to the other nations first. The gemara in Avodah Zara (2b) has the girsa that HKBH went to all teh nations. However there is another girsa that says HKBH went to Eisav and Yishmael. This is based on the possuk in V'Zos HaBeracha of 'v'zarach misa'ir lamo...". I haven't found where this girsa is but I saw it quoted from a Zohar in Balak. (derech agav if anyone knows where this ma'amar is please let me know).

Anyway, over Yom Tov someone commented to me that the nations that HKBH went to were specifically Eisav, Yishmael, Amon and Moav. This person wanted to say that the reason these nations were chosen is because these nations are not part of the 70 nations. The 70 nations were defined at the Dor Haflagah and these nations didn't exist until afterwards.

This leads me to my question. (Actually 2 questions)

a) Is there such a ma'amar Chazal that HKBH only went to Eisav, Yishmael, Amon and Moav. The gemara in AZ mentions all the nations and the Zohar I saw quoted only mentions Eisav and Yishmael.

b) Is true that Eisav, Yishmael, Amon and Moav are not part of the 70 nations. Intuitively it doesn't make sense to say they are excluded from the 70 nations, but m'sevarah it seems they are not part of the 70 nations. To add to this question, there is a GR"A that writes that Eisav was the head of 35 nations and Yishmael the head of the other 35. This is based on the posuk "eileh varechev v'eileh basusim", eileh= 1+35. This implies that in fact Eisav and Yishmael are not part of the 70 nations. But I am not sure if I am remembering the GR"A accurately and it could be the GR"A means they are part of the 70 but they are the leaders. Also. what about Amon and Moav?

Furthermore, the Ramchal in Derech Hashem writes that the spiritual status of the 70 nations was sealed at the Dor Haflagah. As a chesed at Mattan Torah, HKBH opened up the opportunity for them to improve their status by offering them the Torah. Again, how does Eisav, Yishmael, Amon and Moav fit in to this if they were not around by the Dor Haflagah.

Any suggestions?