1)
Why does it say "va'Yeshev b'Ninveh"?
1.
Rashi: This was the capitol of the kingdom - "Min ha'Aretz ha'Hi Yatza Ashur va'Yiven Es Ninveh" (Bereishis 10:11).
2.
Radak (Melachim II, 19:36): He did not go out to war again.