1)
What is the significance of "va'Yikach Bo'az"?
1.
Malbim: He did not do like one who does Yibum, who he acquires her through Bi'ah. Kidushin of money or a document do not acquire [mid'Oraisa], just like they make a Ma'amar mid'Rabanan. This Yibum was only based on custom. He was Mekadesh her with Kesef or a document - va'Yikach, and "va'Tehi Lo l'Ishah" before "va'Yavo Eleha."
2)
Why does it say "va'Yiten Hashem Lah Herayon"?
1.
Malbim: It was Hashgachah that she became pregnant right away, even though she did not give birth from her first husband, who was young.
