1)
Why does the Torah need to mention the fact that they caught up with Yisrael in front of Ba'al Tz'fon?
1.
Rashi (in Iyov, 12:23): Because when Par'oh saw Yisrael encamped in front of Ba'al Tz'fon, 1 he thought that Ba'al Tz'fon agreed to drown Yisrael in the sea, to conform to their original decree to drown all the baby boys that are born in the river.