1)
Why does it say "Hashem"? All these verses from verse 55 speak to Hashem!
1.
Palgei Mayim: It says "Cherpasam Hashem", for they revile in order to revile Elokim Chayim.
2)
Why does it say "Kol Machshevosam Alai"?
1.
Rav Sadya Gaon: All their plans are against me.
2.
Ibn Ezra, Palgei Mayim: They are for my evil.