Why does it say "Ra'av v'Chayah Ra'ah v'Shikeluch"?
Radak: Hunger and evil beasts will kill your children. Minors cannot bear hunger like adults. Also beasts rule over minors more than over adults, for adults contest them with weapons. Also the Torah says "v'Hishlachti Vachem Es Chayas ha'Sadeh v'Shikelah Eschem" (Vayikra 26:2). Beasts and hunger will rule also over adults, just more over minors, therefore it says v'Shikeluch (they will make you childless).
Why does it say "va'Dam Ya'avor Bach"?
Radak: This is the enemy's sword that was not initially intended for Yisrael, like Pharaoh Necho (he merely wanted to pass through Eretz Yisrael in order to fight elsewhere). This is why it says "Ya'avor Bach." Refer to 5:17:3:1.
Why does it say "v'Cherev Avi Alecha"?
Radak: This is the enemy's sword that was intended for Yisrael, like Sancheriv and Nebuchadnetzar. This is why they left their lands! It says "Avi", for Hashem aroused their spirit to come against Yisrael.
Why does it say "Ani Hashem Dibarti"?
Radak: Since I spoke, I must fulfill, and I have the ability to fulfill.
