1)
Why does it say "Dom la'Shem v'Hischolel Lo"?
1.
Gitin 7a: If people bother a person, he need not take action. Wait silently for Hashem, and He will make your enemies fall Chalalim Chalalim (piles of corpses).
2.
Zevachim 115b: Aharon was silent [when he heard that his sons died], and was rewarded - "Dom la'Shem
2)
Why does it say "Al Tischar b'Matzli'ach Darko
1.
Radak: If you have an affliction, and you see a Rasha succeeding and doing his intents, do not mingle with him and learn from his deeds. Hope to Hashem, and He will remove you from [harm from] him.