Why does it say "va'Yishma Aleihem" (with an Ayin)?
Radak: This is like Aleihem (with an Aleph. Often Al (with an Ayin) means El, e.g. "va'Yelech Elkanah ha'Ramasah Al Beiso" (Shmuel I, 2:11) is like El Beiso. Va'Yishma implies that they asked him to show to them, and he agreed. Targum Yonasan implies like this.
What is "Beis Nechoso"?
Rashi: It is where fragrances are hidden, like "Nechos u'Tzri va'Lot" (Bereishis 37:25).
Radak: It is Beis Chemdaso, i.e. everything [desirable] that he has. Afterwards the verse details what were the desirable things. Also "Nechos u'Tzri va'Lot" (Bereishis 37:25) is something desired.
Radak citing Sanhedrin 104a #1: His own wife gave them to drink.
Radak citing Sanhedrin 104a #2: He showed them iron that can shatter iron.
Radak citing Sanhedrin 104a #3: He showed them his treasure house.
What is "Shemen ha'Tov"?
Rashi #1: Some say that it is Shemen ha'Mishchah.
Rashi #2: Some say that it is balsam oil, which is found in Eretz Yisrael - Yehudah v'Eretz Yisrael Hemah Rochlayich b'Chitei Minis u'Fanag" (Yechezkel 27:17). Sefer Yosifun says that Panag is balsam; it grows [Radak - only] in Yericho, which is called Yericho due to the Rei'ach (smell).
It already said that he showed everything to them. What does "Lo Hayah Davar..." include?
Rashi: The Aron, Luchos and the Sefer Torah.