What is the significance of "Kaf Achas Asarah Zahav"?
Ramban (2, from Bamidbar Rabah 13:14): It corresponds to the 10 generations from Peretz (Yehudah's older twin son) until David, all of whom were Tzadikim.
Hadar Zekeinim (19) #1: This hints to Aseres ha'Dibros, which Hashem gave to Moshe, Hand to hand.
Hadar Zekeinim (19) #2, Moshav Zekeinim citing R. Yehudah ha'Chasid: Kaf Achas, i.e. one of the 100 (the Gematriya of Chaf) Brachos that one must bless every day, is worth 10 gold pieces. Da'as Zekeinim - this is a source that 40 gold pieces is the value of Birkas ha'Mazon (Chulin 87a), for it has four Brachos.
Moshav Zekeinim (20, citing Chagigah 23b): The Torah made everything in the spoon one (if Tum'ah touched part, it is all Tamei). 3
What is the significance of "Mele'ah Ketores"?
Rashi (20, citing R. Moshe ha'Darshen): The Gematriya of Ketores 1 is 613, the number of Mitzvos.
Ramban (2, from Bamidbar Rabah 13:14): The 10 generations from Peretz until David were full of good deeds, like the smell of the Ketores.
Hadar Zekeinim (19): When the Torah was given the entire world was filled with fragrances.
Rashi: If one exchanges 'Kuf ' for a 'Dalet ' - via the method of "A-t, Ba-Sh, Ga'R, Da'K" (the first letter of the Aleph Beis is switched to last letter, the second is switched to the second to last...)
On what grounds was he permitted to bring Ketores Nedavah, and on the outer Mizbe'ach?
Rashi: It was a temporary ruling (confined to that occasion). 1
Ramban: To permit them to inaugurate the Mizbe'ach with all the types of Korbanos.
Chagigah 23b learns from here that the Torah made everything in the spoon one. Why don't we learn this from "Ka'aras Kesef Achas" in the previous verse?
Moshav Zekeinim (20, citing Ri): The bowl was full of a Minchah mixed with oil, which is like a liquid. Obviously, it is all one regarding Tum'ah! The Chidush is for dry matters, like Ketores.
Moshav Zekeinim #1: We cannot learn from "Mizrak Echad", for it is not extra. Mizrak can be plural. Perhaps each weighed 70, and "Sheneihem Mele'im" means the bowls and buckets! "Kaf Achas" is extra, for "Mele'ah Ketores" shows that there is only one. 1
Moshav Zekeinim #2: We learn from "Achas Mele'ah Ketores" - just like it is one, it makes [all the Ketores] one.
Moshav Zekeinim: We should say that "Ka'aras Kesef Achas" is extra, for "Mishkalah" is singular! It is better to learn from "Kaf Achas", for Achas is next to Kaf, without any word in between.