Why will they fear His name from west and east?
Radak: After He will pay Gemul, the entire world will fear Him. It is because the Tzar (Gog and Magog) will come in Eretz Yisrael quickly, like a river, and Ru'ach Hashem will eradicate him from the world.
Malbim: Shem Hashem is what is heard from afar. Kevod Hashem is seen from close. This will be seen in the east, where the 10 tribes were exiled - "mi'Mizrach Avi Zar'echa umi'Ma'arav Akabetzeka" (43:5). The miracles and wonders will be revealed there first. The Go'el will be revealed in the east - "Mi He'ir mi'Mizrach Tzedek Yikra'ehu l'Raglo" (41:2). In the west are Bnei Yehudah and Binyamin; they will only hear.
What will come like a river?
Rashi: Affliction, to His enemies. (Refer to 59:20:1:1).
Radak citing his father: Yavo is an expression of sunset, like "u'Va ha'Shemesh v'Taher" (Vayikra 22:7). The afflicter will set and not be seen again, just like a river enters the sea, and it is not seen.
Radak citing Targum Yonasan: Those who pain you (Malbim - the camp of Gog and Magog). Ru'ach Hashem will raise it like a river, to raise the clamor of its waves - "v'Shisheisicha v'Ha'alisicha mi'Yarkesei Tzafon" (Yechezkel 39:2).
What is the meaning of "Nosesah Vo"?
Rashi #1: [Hashem will do] wonders to him. Nosesah is an expression of Nes (miracle).
Rashi #2: They will consume him, like a worm consumes wood. This is like "ki'Msos Noses" (10:18).
Radak #1: It is an expression of Nisah (fleeing). Ru'ach Hashem will make flee the afflicter who does not fear. It is a four-letter root, based on Nos.
Radak #2: It refers to a flag. Normally, the flag bearer is first to strike the opposing army. Ru'ach Hashem will strike the army of Gog and Magog.