Why does it say "Sam Gafni l'Shamah"?
Radak #1: This is past tense used in place of future.
Radak #2: When the locusts come, the resident of the land will say 'it made my vine desolate.' The same applies to "Goy Alah Al Artzi" (6).
Malbim: It destroyed the vine and fig tree via removing the peel from the tree.
Who says "u'Se'enasi"?
Radak #1: All the suffix pronouns (the Yud, i.e. my) refer to the resident of the land.
Radak #2: These are the Navi's words. Yonason translates like this.
What is "li'Ktzafah"?
Rashi, Targum Yonasan: It is disappointment.
Radak #1: It is for anger and a curse.
Radak #2: It is for a peel, and similarly "k'Ketzef Al Pnei ha'Mayim" (Hoshe'a 10:7). The locusts will remove the peel, and eat it.
What is the meaning of "Chasof Chasafah v'Hishlich"?
Rashi: Peeling peels (bark) off the tree, until the vine branches are white.
Radak #1: The suffix pronoun (at the end of Chasafah) is of the fig tree and the vine. The same applies to "Halbinu Sarigeha." Chasof is revealing - it removed the peel [and revealed the white underneath]. Targum Yonasan is like this; it cast the peel to the ground via eating the moisture between the tree and the peel.
Radak #2: It ate the rings 1 and cast the unripe grapes to the ground - it is revealed.
I.e. clusters of ripe grapes. (PF)
Why does it say "Halbinu Sarigeha"?
Radak: After the locusts suck the moisture, the vine sprigs are white and dry. Halbinu is Po'el Omed (the action applies only to the subject), like "ka'Sheleg Yalbinu" (Yeshayah 1:18).