1)
Why does it say "Lachen"?
1.
Radak, Malbim: Since you did not supervise what they are doing, if it is good or bad, and you should have known that it is sinful - they are cast to sin and exiled. For not supervising them, I will visit on you the evil of their deeds.
2)
What is the meaning of "Hafitzosem Es Tzoni va'Tadichum"?
1.
Malbim: Through you, a man was separated from his brother, and you cast them from their place to exile.
3)
What is the meaning of "Lo Fekadtem"?
1.
Rashi: You were not careful to guard them.
2.
Malbim: You did not prevent loss of them via evil beasts. I.e. through you, they were divided into factions, and afterwards went to exile and were killed in wars.
