Rashi #1: It is a balcony. They used to weave it with long and short planks. It has many holes, like a Sevachah (net).

Rashi #2: It is a spiral staircase, like I explained "uv'Lulim Ya'alu" (Melachim I, 6:8).

Radak: It is an Arubah (a hole in the ceiling via which one ascends to the Aliyah). They weave horizontal and vertical planks over it, and leave holes to illuminate the room below. It is like a Sevachah (net).

Rashi: It is an expression of illness. Radak - it is from the root Chalah, just like "va'Ya'al" (Shmuel I, 2:6) is from the root Alah.

Malbim: He saw that Ba'al did not answer him, so he sought new gods. He sought Ba'al Zevuv, even though it is a sign of death. Its priests would prophesize who will live and who will die.