What did Hashem mean when He said "ve'Atah Hanichah Li"? Was Moshe holding on to Him?
Rashi: He was insinuating that, if Moshe would intervene on behalf of Yisrael and Daven for them, He would not destroy them.
Ramban, Targum Onkelos and Targum Yonasan: Hashem meant that Moshe should let Him destroy Yisrael in His anger and not Daven to stop Him. 1
B'rachos, 32a: Moshe did indeed take hold of Hashem (Kevayachol), 2 like a person takes hold of his friend's garment, and declares 'I won't leave You until You pardon them!'
What was Moshe's objection to Hashem's statement "Ve'e'eseh oscha le'Goy Gadol"?
Rashi (in Pasuk 13 - citing B'rachos, 32a): Moshe countered that if a three-legged chair (the merit of the Avos) did not stand before Hashem, how would a chair of one keg be able to? 1
B'rachos 32b: He explained that he would be embarrassed before his ancestors who would accuse him of requesting greatness for himself 2 and failing to Daven for mercy on behalf of Yisrael.
How did Hashem intend to destroy Yisrael?
Ramban (according to Kabalah): He would leave His Midas Rachamim aside, and allow His Midas ha'Din to destroy Yisrael. 1
Rosh (in Pasuk 7): Through the five damaging angels that descended - Af, Ketzef, Cheimah, Hashmed and Mashchis. 2
Ramban: Hence in Pasuk 11, Moshe Davened to "P'nei Hashem Elokav" (the Midas ha'Din, since Hashem had discarded the Midas Rachamim.
Rosh, Ibid.: Moshe then mentioned the three Avos, and the last three departed. Moshe asked Hashem to stand in front of (block) Af ("Kumah Hashem be'Apecha" - Tehilim, 7:7), whilst he himself stood in front of Cheimah ("Lulei Moshe... Lehashiv Chamaso" - Tehilim 106:23), and the Gemara in Nedarim, 32a states that Moshe killed Cheimah.
