1)
Will the sea thunder?
1.
Radak: This is a metaphor.
2.
Malbim: Hashem will split the sea, like he did at the time of Yetzi'as Egypt.
2)
Also above (96:11), it says "Yir'am ha'Yam." That verse begins "Yismechu ha'Shamayim v'Sagel ha'Aretz." Why is this omitted here?
1.
Malbim: Now, conduct via the Ma'arachah will be Batel. There will not be Gilas ha'Aretz, for the general Hashgachah will cease; there will be personal Hashgachah.
3)
Why does it say "Tevel v'Yoshevei Vah"?
1.
Malbim: The Hashgachah will not be in the entire land, rather, in Tevel (the settled part).