1)
Why does it teach that their swords will enter their hearts and their bows will be broken?
1.
Radak: Their swords will kill them, the opposite of their intent. Their bows will be broken - they will not be able to harm the Aniyim and travelers, like they plotted.
2.
Malbim: This explains why Hashem smiled (verse 13) - He knew that this will be their end.