What does "Vayatzeil Elokim ... es Tzon Avichem" mean?
Targum Yonasan: It means 'Hashem emptied your father's sheep'.
What is "va'Yatzel"?
Tosfos ha'Shalem (1, citing R. Efrayim): Hashem saved [the property from belonging to a Rasha, and gave it to a Tzadik].
Rashbam, Bechor Shor: Hashem separated [from Lavan's flock and gave to me].
Why does it say "Avichem" (masculine)?
Ha'Emek Davar: Hashem made the flock multiply tremendously, unlike nature. His Hashgachah caused that you inherit, like a male.