Why does the Torah not describe the Paroches as "Paroches Kodesh" like it did in Pasuk 6?
Rashi: It can be compared to a country that rebels against the king, As long as only a minority rebel, his entourage remains intact; when they all (or the majority) rebel, his entourage falls apart. So it is here, as long as only the Kohen Gadol has sinned, the Kedushah of the Mikdash is not affected; but when the entire Tzibur sins, Chas v'Shalom, it departs.
What was the significance of the staff? Why did Hashem instruct Moshe to take it with him on his Sh'lichus?
Seforno: It was a stick of rulership, the medium through which Moshe was able to override the laws of nature via his command.
Bearing in mind that Hashem had only performed one sign to date (See earlier, Pasuk 4), to which signs is Hashem referring here?
Rashi (in Pasuk 21) and Ramban #1: To the signs that He would teach him shortly. 1
Ramban #2: When earlier in the Parshah (Shemos 3:2), Hashem referred to all the wonders that He would perform in the midst of Egypt, He presumably told him what they were. And those are the signs that He is referring to here. 2