1)
Where did he go?
1.
Malbim: It seemed to him that he entered via the opening [and saw every idolatry engraved on the wall].
2)
What is "Sheketz"?
1.
Rashi: They are [images] made for idolatry, which is Shikutz (detestable).
3)
What is "Mechukeh"?
1.
Rashi: It is engraved on the wall. Radak (7, 10) - this is like Mechokek. Mechukeh is singular, for the Klal. Among the idols of Beis Yisrael are the men engraved in the wall - the idols of Kasdim mentioned below in the Parashah of two women (23:14); they worshipped them.