Why does it say "Habitu El Avraham"?
Radak: Now it explains the parable. Look to [Avraham and Sarah], and go in their ways, and see what I did for them.
Malbim: Just like he was an individual and stood against many who erred, so you will be.
What is the meaning of "Techolelchem"?
Rashi (1-2): She gave birth to you. This is like 1 "Ki Chalah Gam Yaldah" (66:8). Radak - future tense is used in place of past, as if it says Cholelah Eschem.
Malbim: This corresponds to Makeves Bor Nukartem. Sarah should have been sterile based on nature; she bore children 2 against nature. Also you, based on nature, you cannot return the Nochrim to Emunah [in Hashem]; you will do against nature.
Radak: It is like "Chil ka'Yoledah" (Yirmeyah 6:24)
This is like the opinion (Bava Basra 16b) that Avraham had a daughter. Or, "Banim" applies even to one, like "u'Vnei Dan Chushim" (Bereishis 46:23) (PF)
Why does it say "Ki Echad Kerasiv"?
Rashi: He was alone in Eretz Kena'an; I exiled him there from his land and birthplace. Kerasiv - I raised and elevated him. This is like "Keru'ei ha'Edah" (Bamidbar 1:16). Just like he was alone and I raised and elevated him, so I will elevate you, for you are individuals to Me.
Radak: I told him "Lech Lecha me'Artzecha umi'Moladtecha" (Bereishis 12:1). He was one, and afterwards I blessed him and increased him.
Malbim #1: When I called him to publicize Emunah in Me, he was an individual in the world who believed in G-d of the world 1 .
Malbim #2: His nature was to be one and not multiply 2 .
Shem was "Kohen l'Kel Elyon" (Bereishis 14:18)! He and Ever had a Yeshivah in which Yakov learned! Perhaps Malbim means that at the time, Avraham did not know anyone else who believed in Elokei Olam. (PF)
Why does it say "va'Avarechehu v'Arbehu"?
Radak: Future tense is used in place of past.
Malbim: I blessed him, that he was able to return many to believe in Kel. I increased him, to beget children.