From where did Moshe get the idea to make the test with the Ketores?
Ramban #1: It was his own idea.
Ramban #2 (citing the Ibn Ezra): Refer to 16:4:1:2.
On what pretext did Moshe postpone the test until the following day? What was his real motive?
Rashi: He told them that now was a time of drunkenness
Why does the Torah see fit to state "el Korach ve'el Kol Adaso"?
Seforno: Moshe was informing them that he saw through their plot and realized that the rebellion was pre-planned and not spontaneous. 1
Why did he mention specifically "Boker"?
Rashi: Moshe was hinting here that, just as it impossible to change morning into evening, so too, is it impossible to nullify the Kehunah from its current format. 1
Rashi: Seeing as, with reference to both issues, the Torah uses an expression of 'Havdalah'
Who are "es asher Lo" and "ve'es ha'Kadosh" respectively, referring to?
Rashi, citing Midrash Tanchuma and Targum Onkelos), Ramban and Targum Yonasan: They refer, respectively, to the Avodas ha'Leviyah and the Kehunah Gedolah. 1
Seforno: Moshe was telling them that Hashem would make known the one who is speaking in honor of Hashem and the one who is holy and worthy of bringing Korbanos before Hashem.
Which the tribe of Re'uven and Korach respectively were agitating for. See Ramban.
And why did he then add "ve'eis asher Yivchar bo Vehikriv eilav"?
Ramban: He was adding that the one whom Hashem will choose will be the Kohen Gadol not only now, but for all future generations. 1
Seforno: He was warning them that he (the one whom He chooses) alone will emerge from the carnage that is about to take place. 2