1)
Why does it say "Osif Alav"? He discusses what he himself will do!
1.
Radak #1: It means, I will put a heavy yoke on you like my father 1 made heavy, and I will add to it (his yoke). 'Like my father' is omitted.
2.
Radak #2: It means, Hichbid 2 (i.e. my father put a heavy) yoke on you, and I will add to it. The Aleph (in Achbid) is in place of a Hei.
1
In Melachim I, 12:14 it says "my father made your yoke heavy." (PF)
2
In Melachim I, 12:14 it says "Avi Hichbid". (PF)
