If Esav merely thought to himself that he would kill Yaakov, how did Rivkah get to hear about it?
Rashi and Targum Yonasan: She found out about it via Ru'ach ha'Kodesh.
Ramban #1 (citing Ibn Ezra): He passed on his secret to one of his friends, and Rivkah got wind of it.
Ramban #2: "Said in his heart" doesn't necessarily mean that he did not speak it out. It means that he came to a decision, irrespective of whether he verbalized it or not. 1
Oznayim la'Torah: Rashi cites the Midrash, "he has already drunk a cup of consolation over you." Oznayim la'Torah takes this in the literal sense.
Oznayim la'Torah: As the Gemara says (Eruvin 65a), 'Nichnas Yayin, Yatza Sod.'
Why did Rivkah have to send for Yaakov? Where was he?
Ramban: Yaakov had left home and was hiding from Esav (who was crying for revenge) - either out of embarrassment or out of fear.
What does "Misnachem Lecha" mean?
Rashi #1: Regretting the brotherhood, he now considers you a stranger, and is out to kill you.
Rashi #2 and Ramban: He is comforting himself over your death (as in his eyes, you are already dead. 1
Rashi #3: He is consoling himself over the Berachos, 2 with your death (which he is planning to bring about).
Targum Onkelos and Targum Yonasan: He is lying in wait 3 for you, with the intention of murdering you.
Ha'amek Davar: He [pretends] to regret the hatred, and seeks love, in order to kill you.
Seeing as Esav planned to kill Yaakov only after his father's death, why did Rivkah arrange to save Yaakov already now?
Ramban #1, Ohr ha'Chayim (to 27:43): In case Yitzchak, who was already old, died suddenly and Esav acted immediately.
Ramban #2, Ha'amek Davar: Maybe an opportunity would arise to kill Yaakov, which Esav would not hesitate to exploit - even though his father was still alive. 1
Ohr ha'Chayim (to 27:43): Anyone can die any day. This is why Chachamim said 'repent one day before your death' (Avos 2:10)!
Indeed, the Midrash says that he promptly sent Elifaz to kill him, in Yitzchak's lifetime! (PF)
Why does it say "Benah ha'Gadol" and "Benah ha'Katan"?
Ohr ha'Chayim, Malbim, Ha'amek Davar: Big and small refer to ability; Esav is able to do like he plots.
Why does it say "Achicha"?
Malbim: He is your brother - you cannot guard yourself from him.
QUESTIONS ON RASHI
Rashi writes: "Misnachem - He is reconsidering your brotherhood... has already accepted consolation over your death... consoles himself over losing the blessings...." So how does Rashi explain the word?
Gur Aryeh: In the simple sense, "Misnachem" means to change one's thoughts or approach. Homiletically, it means 'consolation.' Rashi concludes that we may interpret this verse as consolation even in the simple sense.