Why are the B'rachos and K'lolas here presented in the singular - "u'Ba'u alecha Kol ha'Berachos" ... 'u'Ba'u alecha Kol ha'K'lalos" (Pasuk 45), as opposed to those in Bechukosai, which were said in the plural "Venasati Gishmeichem be'Itm" ... "Vehifkadti aleichem"?
Oznayim la'Torah: Because, whereas the B'rachos and the K'lalos are communal B'rachos and K'lalos, here, they are individual, where each B'rachah and K'lalah might fall on Re'uven but not on Shimon. 1
What are the implications of "Vehisigucha"?
Seforno: It implies that the B'rachos will reach you even if you make no effort to attain them.
Oznayim la'Torah: It implies that when it rains, the rain will fall in locations where it is needed, which will not hppen if Yisrael sin after Hashem decreed a bountiful rainfall. 1
See Oznayim lla'Torah.
Why does the Torah repeat "ki Sishma be'Kol Hashem Elokecha"?
Seforno: To teach us that this (the B'rachos will reach you even if you make no effort refer to 28:2:1:1) will come about only if we make 'our Torah is fixed, and our work, haphazard.'