Why did he call him "Chozeh"?
Rashi: You prophesize future events.
Why should he flee to Eretz Yehudah?
Rashi: There is Hashem's Mikdash ? you prophesized in His name!
Radak: Since he saw that Yaravam did not accept his Leshon ha'Ra to kill Amos, he told him to flee to Eretz Yehudah and not prophesize more in Malchus Yaravam, i.e. the 10 tribes, and all the more so not in his capitol, i.e. Beis Kel. Really, Shomron was the capitol of Malchei Yisrael, and also for Yehu 1 and his sons, like it is written. Perhaps because they clung to Chatas Yaravam, i.e. serving the calves in Beis Kel and in Dan, Malchei Yisrael made their royal palaces in Beis Kel, since they went there to serve. Beis Kel was closer to Shomron than Dan; Dan was at the end of Eretz Yisrael. Also Yaravam [ben Nevat], his primary Avodah was in Beis Kel ? "va'Ya'al Al ha'Mizbe'ach Asher Asah b'Veis Kel" (Melachim I, 12:33). That place was chosen from the time of Yakov Avinu. They thought that their Avodah there is accepted more than in other places. It will be like Yerushalayim, for Yakov said "[ha'Zos?] Yihyeh Beis Elokim" (Bereishis 28:22). Also refer to 7:12:3:2.
Malbim: Since he saw that he cannot kill Amos via the king, he wanted to scare him to flee from the land. He said, here you are in danger, lest the king kill you. Further, your Nevu'ah will not accomplish anything here. If you prophesize in order to rebuke the nation and make them repent, this will not succeed here. Prophesize in Yehudah ? there they will let you prophesize and heed your voice, but not here. Also refer to 7:12:3:3.
Even though initially Yehu rejected idolatry, he did not move the capitol. (PF)
Why did he say that he will eat bread there?
Rashi: He said so condescendingly. There they will give to you pieces of bread as wages for prophesizing to them!
Radak: False Nevi'im used to prophesize for pieces of bread and a cup of wine or beer. Amatziyah said that Amos should do so ? he should prophesize in Eretz Yehudah, for there they will feed bread to him if he prophesizes evil for Malchei Yisrael.
Malbim: If you prophesize in order to be fed bread, there they will feed Nevi'im; here, we do not.
