1)
Why does it say "Ashrei ha'Goy Asher Hashem Elokav"?
1.
Radak: They do not believe in the foolish beliefs [in other gods]. Rather, [this nation] believes that Hashem is Elokim, i.e. He judges, conducts and supervises everything. "Elokav" teaches that they accepted Him to be Elokim. They were separated from bad Emunos, and commanded to accept and understand that good and bad come to them from Him, according to their deeds - "Ki Hu ha'Nosen Lechem Ko'ach La'asos Chayil" (Devarim 8:18). On the bad side, it says "Eichah Yirdof Echad Elef
2)
What is the meaning of "ha'Am Bachar l'Nachalah Lo"?
1.
Radak: He accepted them to be the nation of His 'inheritance' - "Es Hashem He'emarta ha'Yom Lihyos Lecha lEi'lokim
