Will he literally bow to him?
Radak citing Targum Yonasan: He will lower himself in front of him, and request his food.
Malbim: Yes, he will bow to the Kohen Gadol. This will fulfill the second curse (your income will be constricted).
What is "la'Aguras Kesef"?
Rashi, from Targum Yonasan: It is to be hired for a Ma'ah (a sixth of a Dinar). Agurah is from the root "Esrim Gerah" (Shemos 30:13). Radak - the Aleph was added. Some say that Agurah is like Agra, the Targum of Sachar (wage).
Radak: For the sake of la'Aguras Kesef.
What is "Kikar Lechem"?
Radak citing Targum Yonasan: It is a piece of bread.
What is the meaning of "Sefacheni"?
Rashi: Gather me.
Radak: Attach me. This is like "v'Nispechu Al Beis Yakov" (Yeshayah 14:1), "me'Histape'ach b'Nachalas Hashem" (below, 26:19).
What are "ha'Kehunos"?
Radak citing Targum Yonasan: They are Mishmaros of Kehunah.