Why is removing the Bamos a reason why Hashem will not save Chizkiyah?
Rashi: He destroyed all the houses, Bamos and Mizbechos of idolatry 1 , and forced all of Yehudah to bow in front of one Mizbe'ach.
Radak (Melachim II, 18:22): He did so only for his own honor, so everyone will come to Yerushalayim. The Bamos were l'Shem Hashem! Malbim - it is more honorable for Hashem that people serve Him everywhere!
Metiv Shir (the Netziv), 5:6: This is difficult. Destroying Bamos of idolatry is a merit! (Rashi holds like he wrote in Melachim II, 18:22, that Ravshake said that Hashem desires [that we do] idolatry. Refer to Melachim II, 18:17:2:1, 18:17:2:1*. - PF)
What is the meaning of "li'Yhudah veli'Yrushalayim"?
Refer to Melachim II, 18:22:2:1.