Until now, he was called Michayhu. Why is he now called Michah?
Malbim (1): Initially he was a Tzadik (and had Yud Kei, a name of Hashem, in his name). After he served idolatry, he is called Michah. Initially it says u'Shmo Michayhu, [unlike] Resha'im, whose name comes first, e.g. "Naval Shmo" (Shmuel 1:25:25). Aveirah leads to an Aveirah - after leaving idolatry in his house, he made a house for it, and made an Efod and Terafim [from his own money], and then appointed one of his sons to be a priest for idolatry.
What is "Beis Elohim"?
Rashi (from Shevu'os 35b): It is a house for idolatry. Every Elokim in the Parshah is Chulin (refers to idolatry), except for (18:31) "Kol Yemei Heyos Beis Elokim b'Shilo."
What is the meaning of "va'Ymalei Es Yado"?
Radak: He offered Korbanos via one of his sons, and appointed him to be Kohen. The same applies to "u'Mileisa Yad Aharon v'Yad Banav" (Shemos 29:9).
