What is the grammatical form of "Haloch"?
Radak: It is Makor (like an infinitive) or a command. The same applies to "Zachor Es Yom ha'Shabbos" (Shemos 20:8), "Tamoch Ashurai" (Tehilim 17:5).
What is "b'Aznei Yerushalayim"?
Radak: It is the nation of Yerushalayim. He mentions the city as if it is the nation.
Hashem is sending Yirmeyah to rebuke. Why does he tell them that Hashem remembers their earlier Chesed and love?
Rashi: He informs them, if you will repent, I desire to have mercy on you!
Radak: Even though I bring evil on you for your bad deeds, I will not finish you off, and I will punish those who do evil to you.
Malbim (1): Know that in spite of all the punishments that will come, Hashem still loves Yisrael and did not forget the Bris of old. He will punish those who do evil to them, like a father who was angry at his son, and told evil men to hit him harshly. He still loves his son, and is angry at the one who hit him, and he will punish him.
What is "Chesed Ne'urayich"?
Rashi (from Mechilta Beshalach 14): It is like the verse continues, Lechtech Acharai ba'Midbar. You followed my Sheluchim Moshe and Aharon, from a settled land to a wilderness, without provisions, for you trusted in Me.
Targum Yonasan: The Chesed of your early days, the love of your fathers, who trusted in Me. Radak - perhaps this refers to Avraham, Yitzchak and Yakov, who were Anshei Chesed. Or, it is Ahavas Kelulosayich; it all refers to Dor ha'Midbar. It is an idiom to call the early days "Yemei Ne'urim", just like people are called Na'arim before they are called Bachurim and Zekenim.
Malbim: The verse compares the initial union of Hashem with His nation to a man who came from afar. A beautiful daughter of an Ashir entered him into her house and did Chesed with him. Her soul clung to him and she married him, and trusted him and left her father's house to go with him to a Midbar, wherever he will desire to go. In the Nimshal, the Avos and their children after them went in Hashem's ways and publicized His Elokus when He was a stranger, not known to the nations, who served idolatry.
What is "Kelulosayich"?
Rashi: It is your Chupah; I brought you in (married you). Radak - at Matan Torah, Hashem and Yisrael were like Chasan and Kalah.
Malbim: It is leaving Egypt and accepting the Torah.
What is "Lechtech Acharai ba'Midbar"?
Rashi (from Mechilta Beshalach 14): This is Chesed Ne'urayich. You followed my Sheluchim Moshe and Aharon, from a settled land to a wilderness, without provisions, for you trusted in Me. Malbim - this was the last of the three stages - before the Shiduch, Shiduchin, and after Shiduchin. Hashem remembers all of these merits of Yisrael!