Why does the Torah switch from "Pekudei ha'Levi" in Pasuk 57 to "Mishp'chos Levi"?
Oznayim la'Torah: It writes "ha'Levi" in connetion with the thre Batei Avos due to the importance of the 'Legion of the King, that was divided into three groups. See answer #2 to the previous question.
Why does the Torah omit the families of Shim'i, Azi'eli, and from Yitzhar, Nefeg and Zichri?
Rashi: Refer to 26:13:152:1. 1
The Pasuk in Divrei Hayamim 1, 23 actually lists th families of Shim'i (in Pasuk 9) and Ozi'eli (in Pasuk 20). See Oznayim la'Torah DH 'Eileh Mishp'chos Levi #2..
Why does the Torah mention "Mishpachas ha'Korchi", which, in Bamidbar (3:27), was part of the family of Yitzhar?
Ramban #1 and Moshav Zekenim #1: Because at that time, Yitzhar also had grandchildren from Nefeg and Zichri; whereas now only Korach's children remained from his family, so that they took over the family name.
Ramban #2 and Moshav Zekenim #2: It was in order to highlight the fact that Korach's children remained alive, and that they were bigger Tzadikim than their father. 1
Why does the Torah not write "Mishpachas ha'Amrami", like it does by all the other families?
Oznayim la'Torah: Because Kohanim also emerged from this family, and the Torah wants to stress the fact that also they are included in "Pikudei ha'Levi".