The source for R. Moshe (question 2) is the new editions of Darash Moshe that have more material on the parshah in the back. He does not say what his source is, or even that it is a midrash, but it is probably the Gemara quoted by Rashi to the passuk (sources)
אמר רב יהודה אמר רב כל מה שעשה אברהם למלאכי השרת בעצמו עשה הקב"ה לבניו בעצמו וכל [מה] שעשה אברהם ע"י שליח עשה הקב"ה לבניו ע"י שליח
Rav Yehuda says that Rav says: Every action that Abraham performed himself for the ministering angels, the Holy One, Blessed be He, performed Himself for Abraham’s descendants. And every action that Abraham performed through a messenger, the Holy One, Blessed be He, likewise performed for his descendants through a messenger.
(בראשית יח, ז) ואל הבקר רץ אברהם (במדבר יא, לא) ורוח נסע מאת ה' ויקח חמאה וחלב (שמות טז, ד) הנני ממטיר לכם לחם מן השמים
The Gemara elaborates: With regard to Abraham, the verse states: “And Abraham ran to the herd” (Genesis 18:7), bringing the meat himself, and in reference to God’s actions for Abraham’s descendants the verse states: “And there went forth a wind from the Lord, and brought across quails from the sea” (Numbers 11:31), that God brought meat to them. In reference to Abraham, the verse states: “And he took curd and milk” (Genesis 18:8), and God says to the Jewish people: “Behold, I will cause to rain bread from heaven for you” (Exodus 16:4), which shows that God gave food to the Jewish people.
(בראשית יח, ח) והוא עומד עליהם תחת העץ (שמות יז, ו) הנני עומד לפניך שם על הצור [וגו'] (בראשית יח, טז) ואברהם הולך עמם לשלחם (שמות יג, כא) וה' הולך לפניהם יומםWith regard to Abraham, the verse states: “And he stood by them under the tree, and they ate” (Genesis 18:8), and in reference to God, the verse states: “Behold, I will stand before you there upon the rock in Horeb; and you shall strike the rock, and there shall come water out of it” (Exodus 17:6). In the case of Abraham it is written: “And Abraham went with them to bring them on the way” (Genesis 18:16), and the verse states: “And the Lord went before them by day” (Exodus 13:21).
(בראשית יח, ד) יוקח נא מעט מים (שמות יז, ו) והכית בצור ויצאו ממנו מים ושתה העםBy contrast, Abraham performed certain actions through an agent. He said: “Let now a little water be fetched” (Genesis 18:4), and correspondingly the verse states in reference to Moses, God’s messenger: “And you shall strike the rock, and there shall come water out of it, that the people may drink” (Exodus 17:6).
