1)
Why does it say "Lachen"?
1.
Rashi: It is an expression of a Shevu'ah.
2)
Why will the youths fall in the streets?
1.
Malbim: It is because the enemy camps around, and they cannot escape.
3)
What is the meaning of "Yidamu"?
1.
Radak: They will be cut off.