1)
Why does it say "va'Teled Lo"?
1.
Perhaps just like we expound "va'Tahar Lo" - Giborim like him, Tzadikim like him (Rashi 38:18, from Bereishis Rabah 85:9), similarly here. (PF)
2.
Until now, he himself did not have sons, only daughters and grandsons. She bore a son to him. (Perhaps this is Malbim's intent. - PF)
