1)
Why does it say "Al Yehi Lo Moshech Chased?
1.
Radak: Since it said that his children will go around begging for bread, it says that will not be found one who will do Chesed to his sons due to him. No one will have mercy on his sons.
2.
Malbim: They will not find help via the Chesed that their father did for Ploni, that Ploni will help his sons; no one will have mercy on them.
2)
Why does "v'Al Yehi Chonen li'Ysomav" add?
1.
Malbim: Also, they will not find help via grace; no one will have grace on them.