Mivaksheyemes
The Netziv answers both of your questions:
1. In Avodim Hoyinu: the words “biyod chazoko” refers to the fact that the 4/5 did not want to go out – so Hashem had to kill them so that he could take “Binai Yisrael” out.
2. It is only our acceptance of Avodas Hashem that created a Hashgocho Peratis for Bnai Yisrael – which resulted in Hashem interfering with the history of nations for our benefit. All of the occurances in history which resulted in the freeing of slaves, was a result of this “hashgocho peratis” which resulted from yetziyas mitzrayim. If this had not happened, then we would still have been slaves.