1)
Why does it say "Berok Barak"?
1.
Radak: When the verb comes with (resembles) the noun, it strengthens the matter. This is like "Kol Bogedei Vaged" (Yirmeyah 12:1), "u'Ma'alah Ma'al" (Vayikra 5:21) and similar verses.
2)
Should Hashem literally send lightning and arrows?
1.
Radak: These refer to decrees from Shamayim.
2.
Malbim: Yes - if You want to appear only via a Shali'ach, send lightning, which is light that emanates from You, and it will scatter them; they will see that the Shali'ach comes from You. If You do not want to send lightning, a spark of Your honor, send Your arrows and confound them. The arrow should be Yours; it will suffice to destroy them.
