"Lifnei HaSh-m" is not mentioned anywhere else in the Parshah. Why did Rivkah insert it specifically here?
Rashi and Rashbam: He meant that he would bless him with HaSh-m's consent. 1
Ramban: Rivkah was telling Yaakov that the Berachah that his father intended to give Esav was given with Ru'ach ha'Kodesh, and should it go to Esav, it will be forever and that he (Yaakov) will be doomed.
Malbim: She told him, do not say that the Berachah will not help, for he intends for Esav. Nevu'ah is only to reach HaSh-m's desire. If HaSh-m puts in his mouth to bless you, Yitzchak's intent for Esav will not hurt, just like one who mistakenly seeded barley. Barley will sprout in spite of his error! Yitzchak is merely the conduit for HaSh-m's Berachah.
Thereby turning it into a Divine blessing. (Even though the Torah does not record that Yitzchak said so, as the Yerushalmi says in Rosh Hashanah 3:5, "the words of the Torah are poor in one place and rich in another." - EC)
Yitzchak had said "va'Aseh Li Mat'amim... v'Havi'ah Li." Why did Rivkah switch the order?
Ha'amek Davar: Indeed, Yitzchak commanded Esav to bring the animal alive to Yitzchak's house, and prepare it there. (Do not worry lest he bring promptly what was already prepared.) Perhaps Yitzchak normally did not rely on what was cooked in Esav's house, for his wives were suspected to make him stumble in Isurim.
Why is there a Hei at the end of "va'Avarechecha"?