1)
Why does it say "v'Hachinosi Es Malchuso" in verse 11, and "v'Chonanti Es Kis'o" here?
1.
Malbim (Shmuel II, 7:13): Hachanah is the start of the kingship, and Konenus finishes the building of it.
2)
Why does it say "Ad Olam" three times (here, and verses 14, 22)?
1.
Vilna Gaon: One is in this world, one is in the world to come, and one is in Yemos ha'Mashi'ach.
