1)
Does "Ki" explain the reason for the previous verse?
1.
Malbim: Yes. The Egyptians were happy to send us, and left everything in Yisrael's hands
2)
Where do we find that the Egyptians were afraid?
1.
Radak: "Ki Amru Kulanu Mesim" (Shemos 12:33).
2.
Malbim: Even the dogs did not bark (Shemos 11:7; this was due to fear).