To whom does "Ish el Achiv" refer?
Rashi (in Bereishis 49:5) and Targum Yonasan: It refers to Shimon and Levi, who were brothers-in-arms - from the time of the episode with Shechem.
Why did they refer to Yosef as "Ba'al ha'Chalomos ha'Lazeh"?
Seforno 1 : They accused him of deliberately relating his dreams in order to provoke them into attacking him, so as to incur the wrath of their father, of Hashem or both, thereby brining about their destruction.
Oznayim la'Torah: Because of all the things that irked them - the fact that their father loved him more than them, that he made him a special robe and the Lashon ha'Ra that he spoke about them to their father, the dreams, that suggested that he wanted to rule over them, angered them the most.
Ha'Emek Davar: "Ha'Lazeh" refers to something exceptionally awesome, in this case, his dreams.
Who issued the suggestion to dispose of Yosef?
Rashi (49:5) and Targum Yonasan: Shimon and Levi, who were comrades-in-arms. 1
Why does it say "Ba'al ha'Chalamos ha'Lazeh Ba?!
Malbim: He did not come to see the Shalom of his brothers, rather, to fulfill his dream and rule over them in the field.