1)
Why did He say that he put iron rods in place of the wooden sticks?
1.
Radak: The Motos are straps or sinews used to tie a yoke on the animal's neck. Chananyah broke the yoke, which was of wood. Also "Motos Barzel" are straps and sinews used to tie an iron yoke on the animal's neck.
2.
Malbim: Via wanting to break the stick and rebel, an iron yoke will be put in place of it, and [Nebuchadnetzar] will subjugate them even more.
