Considering that the angels presumably knew the members of Lot's family; what else did they mean when they asked him, "Od Mi Lecha Po"?
Rashi: Now that the Sodomites did this disgusting thing, do you still have something to say in their defense?!
From the fact that the Pasuk says nothing about Lot speaking with sons to leave Sedom, why does the angel mention 'sons' here, as Rashi explains?
Ramban (explaining Rashi): The angels spoke like human-beings, who would have mentioned sons on the assumption that he may have had sons.
Ramban (citing Ibn Ezra): The angel meant sons-in-law, who are like sons.
Ramban: In fact, Lot had sons living in town. However, convinced that they would listen to him to leave without fuss, he first approached the two men who were betrothed to his two unmarried daughters, who mocked him and argued with him until close to dawn-break, at which point the angel allowed him to save only those members of his family who were with him at home when he left the house.
In any event, to whom were the angels referring when they added, "and whoever you have in the town"?
See Targum Yonasan, who omits it completely from his translation, but adds 'a relative or a brother' before 'sons-in-law.'
On what merit was Lot's family saved together with him?
Ramban #1: On his personal merit, his sons, daughters and sons-in-law were (offered to be) saved. 1
Ramban #2: They were saved because it is correct for a guest to save the host and all his family. 2
How come, after going out of his way to protect his defenseless guests, Lot now begins to take orders from them and to obey their instructions to the letter?
Ramban (to 19:9): At first, Lot thought they were human-beings, who were at the mercy of the Sodomites. He realized they were angels, however, when they struck them with blindness, and from that point on, he took his instructions from them, as the Pasuk goes on to explain.
Who is "Chasan;" is this word in the singular?
Moshav Zekenim #1: Chasan can refer to many Chasanim.
Moshav Zekenim #2: He had one son-in-law in his house who had betrothed his daughter.
Only one of the angels was sent to save Lot! Why does it say that "they said to him"?
Bereishis Rabah asks this question on verses 19: 16,17 - "they took him out... they left him... they took them out," 1 and answers that "he said to him" proves that only one angel saved Lot.
Gur Aryeh: Since Lot was not allowed to save his property, the angel who was destroying was responsible to see that he leave without his money. Refer to 19:16:4.1.
QUESTIONS ON RASHI
Rashi writes: "The entire night, Lot had been trying to defend them." But see Rashi to 18:4; Lot's initial response to the angels was,' The majority are wicked!'
Gur Aryeh: Certainly the Sodomites were wicked; Lot was arguing that they were undeserving of destruction.
Rashi writes: "If you have a son-in-law...." Why does Rashi add the word "if"?
Gur Aryeh: The angel had asked, "Who else do you have here;" this was a continuation of that question.
Rashi writes: "'And your sons' - The sons of your married daughters (i.e. grandchildren)." Why not explain as literally sons?
Gur Aryeh: The fact that Lot immediately went to convince his sons-in-law to leave (19:4) shows that he had no sons, and the angels surely knew this.
