1)
What is the comparison "ki'Smol'ach Kol ha'Aretz"?
1.
Rashi: When I will take My kingship, the land will rejoice - "Hashem Malach Tagel ha'Aretz" (Tehilim 97:1), then I will make you desolate.
2.
Radak: The prefix Kaf here and in "k'Simchasecha" (15) equate them, like "cha'Am ka'Kohen" (Yeshayah 24:2), "Chamocha k'Far'o" (Bereishis 44:18), "ka'Malveh ka'Loveh" (Yeshayah 24:2). The Simchah of the entire land over your desolation equals your Simchah over the desolation of Nachalas Yisrael.
3.
Malbim: I will make you desolate when the entire land will rejoice over Yisrael dwelling in Simchah and serenity. You will see their Simchah before your fall.