What is the meaning of "Lo ch'Eleh Chelek Yakov"?
Radak: These gods are [the Nochrim's] portion. Yakov's portion is different - He formed everything; Yisrael are His inheritance. We will not serve anything other than Him, for He formed everything; nothing is formed or created without Him. He chose Yisrael for an inheritance to serve Him, and He will be their portion. Even though we were exiled, we did not abandon Him. Because we abandoned Him in our land, we were exiled from it! We recognize this, and thank Hashem Tzevakos - the Master of legions above and below. It is proper to serve the Master, and not the stars, which are His legions. All this Yirmeyah sent to Chachmei Yisrael in Galus Bavel; they were exiled with Yehoyachin. So they should answer the Bavliyim if they want to entice them to serve idolatry.
Malbim: This refers to why we should not learn the way of the Goyim, for Yakov's portion is different. Even [other gods'] worshippers know that they don't form - Hashem is the [only] one who forms. Even the worshippers think that [each god] is appointed only over one matter - Hashem forms everything!
Why does it say "Yotzer ha'Kol Hu'?
Malbim: Refer to 8:16:1:2.
Why does it say "Yisrael Shevet Nachalaso"?
Malbim: We need not fear [other gods], for we are not under the Ma'arachah, only under Hashem, who rules over all the legions to do His will - "Hashem Tzevakos Shmo."
