Why did Lavan mention "Benosai" twice?
Rashi: Because Bilhah and Zilpah were also his daughters - from a concubine.
Why did Lavan decide to add Hashem to the list of witnesses?
Seforno: To warn Yaakov that, in the event that he transgressed the covenant, he would be subject to Divine retribution.
Malbim: Afflicting his daughters (through withholding intimacy) is a hidden matter that only Hashem will know. 1
Why did Lavan say, "there is no man with us"? His brothers were with them!
Hadar Zekenim: They were relatives; there is no one here Kosher to testify.
Moshav Zekenim: He called his brothers 'dogs.' This is difficult. 1
Malbim: There is no man who can testify about afflicting my daughters; it is a covert matter. Hashem must be the witness.
Radak: You will be going to another land; and none [of my men] will accompany you.
What affliction of his daughters did Lavan warn about?
Rashi: Yaakov may not deny them Onah (intimacy at the proper times).
Bechor Shor: He may not make them work too hard.
Tosfos ha'Shalem (5): He may not vex them in various ways.
Tosfos ha'Shalem (1): He warned against unnatural Bi'ah (she'Lo k'Darkah).