Why does it say three times that David fled (verses 10, 12, 18)?
Malbim: First he fled from his house. Then he fled from the guards. Now he fled totally. All the delays (until they realized that he fled) enabled this.
Why does verse 10 say Nas, and here it says Barach?
Malbim: Nas is when one is chased, or danger is near. This is when he was near Sha'ul. Afterwards it was not so dangerous; it says Barach.
Why is it written b'Noyas, and we pronounce it b'Nayos?
Radak: Both of these are the same; they are based on Naveh (habitation).
Why did they go to Nayos?
Rashi: There was a study house there. 1 Radak - Bnei ha'Nevi'im learned in front of Shmuel there.
Radak citing Zevachim 54b: [They were not in Nayos. Rather,] they probed where will be the Noy (beauty) of the world, i.e. the Beis ha'Mikdash.
Yalkut Shimoni (Shmuel, 129): That night David learned from Shmuel more than a [regular] Chacham learns in 100 years. Lev Eliyahu (Bereishis p.98) - this shows David's Gevurah in learning Torah. Even though he was in mortal danger and feared for his life, and was ready to flee in a moment if Sha'ul will catch him, he was able to learn so much and so deeply!
