Why did he say "Mi Shemecha" (and not Mah Shemecha)?
Radak: We say Mah Shemecha about a person, because the name is not the person himself. However, Mano'ach did not know that he is an angel! He thought that he is a great Navi, who is known by his name to one who did not see him, so the name is like the person himself.
What is the meaning of "Ki Yavo Devarcha v'Chibadnucha"?
Rashi: If you will send to us a Shelichus, if we recognize that it is in your name, we will do what you tell us.
Radak citing Targum Yonasan: When your word will be fulfilled, we will honor you. Malbim - Mano'ach thought that a Navi will exert himself to go to tell a prophecy only if he will receive money, food or honor. 1 Since he did not want food, he thought that he wants honor. For this, Mano'ach must know his name, so when the prophecy comes true, he can publicize who predicted it.
This is like Malbim explained above (verse 13), that Mano'ach was an ignoramus. (PF)
