Why was Moshe angry?
Rashi (in the original text, cited in Moshav Zekenim citing the Tanchuma): It does not mean angry; it means that he was deeply pained - because he had no answer to their accusation that he did not keep his word about bringing them to Eretz Yisrael. 1
Ramban #1 (on Pasuk 16): Moshe's anger burned - (as Targum Onkelos and Targum Yonasan explain) - because Dasan and Aviram said "Lo Na'aleh". 2
Ramban #2: Refer to 16:29:1:1**.
Rashi (in the original manuscript) and Hadar Zekenim (on Pasuk 6) both citing the Tanchuma): When one disputes with another, if he answers him, he is pleased. If the other is silent (he refuses to respond), he is pained.
Which Minchah was Moshe referring to?
Rashi #1: He was referring to the Ketores that they would bring the following day. 1
Rashi #2: He was referring to the individual portion that each person has in the Korban Tamid. 2
Ramban (citing Targum Onkelos): Seeing as they wanted the Kehunah and to sacrifice the Korbanos, Moshe davened that Hashem should decline to accept any Korban that they might bring on the Mizbe'ach 3 and any Tefilah that they might offer.
See Ramban's objection to this explanation.
Rashi: He Davened that the fire on the Mizbe'ach should not burn it. See Ramban's objection to this explanation.
What was Moshe referring to when he said "Lo Chamor Echad meihem Nasasi"?
Rashi (citing Targum Onkelos) 1 : He was referring to compensation for transportation - that when he traveled from Midyan to Egypt to take Yisrael out, leading his wife and sons on a donkey, he was entitled to claim the donkey from the people, but in fact, used his own donkey.
Seforno: He meant that he never benefited from any of them, even with regard to borrowing a donkey from one of them. 2
According to Rashi's interpretation of the word "Shecharis" in Targum Onkelos.
Seforno: Something that people commonly do - and this was a sure proof that whatever he did as a leader was for the people's sake and that their claims stemmed from a lack of Hakaras ha'Tov (gratitude).
According to the Ramban's interpretation of the word "Shecharis" in Targum Onkelos.
Rashbam: So why do they accuse him of dominating them?
What did Moshe mean when he concluded "ve'Lo Hare'osi es Achad meihem"?