1)
Why is removing the Bamos a reason why Hashem will not save Chizkiyah?
1.
Rashi (Yeshayah 36:7): He destroyed all the houses, Bamos and Mizbechos of idolatry 1 , and forced all of Yehudah to bow in front of one Mizbe'ach.
2.
Radak: He did so only for his own honor, so everyone will come to Yerushalayim. The Bamos were l'Shem Hashem! Malbim (Yeshayah 36:7) - it is more honorable for Hashem that people serve Him everywhere!
2)
What is the meaning of "li'Yhudah veli'Yrushalayim"?
1.
Radak citing Targum Yonasan: To the people of Yehudah and the residents of Yerushalayim.