1)
Why does it say "Al Beiso"?
1.
Radak: This is like El Beiso. Also "va'Yelech Elkanah Al Beiso" (Shmuel I, 2:11) is like El Beiso; "v'Dibarti Al ha'Nevi'im" (Hoshe'a 12:11) is like El ha'Nevi'im.
2)
What is the meaning of "Sar v'Za'ef"?
1.
Targum Yonasan: Nesis v'Davai (depressed). Rashi - his spirit was Sarah (departed) from him. Radak - also the Targum of "v'Hinam Zo'afim" (Bereishis 40:6) is Inun Nesisim.
2.
Radak: This is like "Mah Zeh Ruchacha Sarah" (21:5); it is close to Za'af (anger).