1)
What is the meaning of "va'Yilfos"?
1.
Rashi: He held, like "va'Yecherad ha'Ish va'Yilafes" (Rus 3:8); he was held in her hands.
2)
Shimshon told the youth "v'Esha'en" (verse 26). Why does it say here "va'Yisamech"?
1.
Malbim: Semichah is with all one's strength, like we say about Semichah on a Korban. She'inah is with part of the body. (Had the youth known that he plans to use all his strength, he would have suspected Shimshon's intent.)