1)
What is the meaning of "va'Yanchem"?
1.
Radak: After taking them across the sea, He led them. The cloud was even before, after they traveled from Sukos.
2.
Malbim: Just like Hashem overrode nature to split the sea, also to supply their needs - leading them via the cloud and fire, and giving water miraculously.
2)
Why was the pillar of fire the entire night?
1.
Radak: It illuminated for them until the light of morning; they did not need a lamp.
