Does he eat in darkness?
Rav Sadya Gaon: He goes 1 in darkness, with many afflictions.
Ibn Ezra, Metzudas David: Yes; he does not eat during the day, for he is too distracted in his toil to gather money.
Ri Kara: He goes 2 in darkness, without Torah, without a lamp, without Mitzvos, without a bathhouse 3 , and without good deeds. Since in this world he lacked a lamp, Torah, Mitzvos and good deeds, so he is buried naked, without a lamp or bathhouse. From here they said that it is a proper custom to bathe the Mes and purify it in hot water, and to light a lamp in front of it. There is a proof for this from Eichah Rabasi.
Seforno: This Ashir does not acquire perfection with his wealth. All his days he eats 4 in darkness, without knowing the path on which eternal light will dwell.
Why did he have much anger?
Rashbam: It was due to his many thoughts while acquiring money.
Seforno: He does not acquire extras like his desire.
Metzudas David: It is due to his many affairs. Since they are many, not all can be like his desire.
What is "v'Chalyo"?
Rashi: It is v'Choli (and illness 1 ). The suffix Vov is extra, like "Chayso Ya'ar" (Tehilim 104:20).
Seforno: This is the illness common among Ashirim - stinginess, like Chazal said 'the rich are frugal' (Menachos 86a). He lives in poverty, in order to die wealthy!
Metzudas David: It is the illness that comes from much anger; from this came Katzef, and it became known to Rabim (refer to 5:16:4:1).
Ibn Ezra: It is illness of the Nefesh, i.e. fear.
What is the difference between Ka'as and Katzef?
Metzudas Tziyon: Ketzef is showing anger externally.