What was Bil'am referring to when he said "Lo Ish Keil Viyechazev"?
Rashi: He was referring to Hashem's promise to bring them to the land of the seven nations of Cana'ani and to inherit it, and Balak wants to kill them all in the desert!
Rashbam: He was referring to the B'rachah that Hashem had conferred upon Yisrael earlier in the day, 1 from which He would not withdraw seeing as Yisrael had certainly not sinned in the interim, so why should He retract?
See Pasuk 10.
And what was he referring to when he said "u'Ven Adam Veyisnecham"?
Rashbam: 'Neither is he human-being, so (by the same token) why should he change His mind?
To whom does "ha'Hu Amar ve'Lo Ya'aseh ... " pertain?
Rashi #1, Rashbam and Targum Yonasan 1 : With reference to Hashem (the subject of the Pasuk), in the form of a rhetoric, it means 'Would He say and not do, speak and not carry out?'
Rashi #2 (citing Targum Onkelos) and Targum Yonasan: With reference to 'Ish' (mentioned ttogether with the subject) 'He says and does not do, promises and does not carry out; 2 But Hashem says and does, promises and carries out!' 3