Why is the 'Kuf' in the word "Katzti" small?
Ba'al Haturim: Because she foresaw that Eisav's descendents (Edom) were going to destroy the Beis-Ha'Mikdash, which was a hundred Amos tall. 1
Ha'amek Davar and Oznayim la'Torah: Because this was not the real reason that she wanted Yitzchak's consent to send Ya?akov away; 2 it was only an excuse. Oznayim la'Torah - it seems that Ya?akov would not leave Eretz Cana'an without his father's consent, so Rivkah fabricated an excuse for Yitzchak to order him to go to Padan Aram.
Ba?al Haturim: By the same token, David Hamelech, in Tehilim (84:4) wrote the word "Ken" in the Pasuk "u'Deror Ken lah") with a large 'Kuf' - because he was requesting that the Beis-Hamikdash (which was a hundred Amos tall) should not be destroyed.
Why did Rivkah not tell Yitzchak the real reason behind the need to send Yaakov to Charan?
Rashbam: She acted wisely in giving the reason that she did without telling him that it was on account of Eisav's hatred. 1
Ohr ha'Chayim: Due to the Isur of Rechilus. She needed to tell Ya?akov to save his life.
Malbim: Because she did not want to pain Yitzchak.
Ha'amek Davar: She did not want to tell him of her fears that Eisav would kill Ya?akov, because she had such awe of Yitzchak that she would not be able to argue with him if he would not listen to her. Refer to 24:62:1:7. 2
Refer to 25:28:4:1 and note. Presumably, based on the fact that Eisav's plans were revealed to her and not to Yitzchak, she realized that Hashem wanted Eisav's enmity to be withheld from him until the day he died, despite the fact that he now knew about his evil. Refer to 27:33:1:1 & 27:33:1:4. Moreover, Eisav knew why Yitzchak sent Ya?akov to Charan and reacted accordingly. Who knows how he would have reacted had Yitzchak sent Ya?akov away to save him from his (Eisav's) hands!
Surely she would not be afraid to tell him information he does not know. However, if he would say 'I know Eisav - he would not really kill him', she would not be able to disagree! (PF)
Why did Rivkah use the double expression "mi'Benos Cheis, mi'Benos ha'Aretz"?
Oznayim la'Torah: Because there were two points against the B?nos Cheis 1 : 1. They were all idolaters who had been raised from the cradle to sacrifice to idols; 2. They lived among their relatives, who would encourage them to keep up their idolatrous practices, rendering it impossible to train them to serve Hashem. 2
Malbim: Even if she would be from B?nos ha'Aretz not from the B?nos Cheis, if she would be like these [the wives of Eisav] ...
Oznayim la'Torah: Both of which Yitzchak mentioned - in 28:1-2 when he spoke to Ya?akov.
Refer to Bereishis 24:3:6:3.
