1)
Having pointed out the distinction between Goshen and the rest of Egypt, why does the Torah need to add, "v'Samti Fedus... "?
1.
Ramban and Seforno: To teach us that a Yisrael was safe wherever he was; inasmuch as anywhere in Egypt, the wild beasts would ignore a Yisrael they saw, but would attack any Egyptian in the vicinity. 1
1
As the Pasuk indicates in Tehilim 78:45.
2)
Why did Hashem set a date for this Makah's arrival?
1.
Maharal: Refer to 9:18:1.01:2 (regarding Makas Barad; which he contrasts with Arov, Dever and Arbeh).
3)
Why, by this plague (and all the subsequent plagues for which there was a warning) did Hashem say it will take place "Machar" - tomorrow?