What is the grammatical form of "Yachel"?
Radak: It is a command. Yisrael, hope to Hashem to redeem you from Galus.
What is the meaning of "Ki Im Hashem ha'Chesed"?
Radak: Hashem's Chesed is constantly with the creations; He will do Chesed with you.
Malbim: Hope to Hashem is not constricted to any time. There is Chesed and redemption with Him; He can redeem you before the destined time, via "He will redeem Yisrael from all their sins" (8). He can remove darkness of night before morning, and redeem them before dawn; if they merit, "Achishenah" (Yeshayah 60:22 - I will rush it) (Sanhedrin 98a).
Why does it say "Ki Harbeh Imo Fedus"?
Radak: He already redeemed you many times - from Egypt, from Bavel and from many afflictions. So He will redeem You from this Galus. He does not lack redemption; much is with Him!