Here "fill his stomach" is a metonym meaning eat a lot. (See: [[rc://en/ta/man/translate/figs-metonymy]])
# God will throw the fierceness of his wrath on him
The "fierceness of his wrath" represents God's anger and punishment. Throwing the punishment on him represents punishing him severely. AT: "God will be angry and throw down his punishment on him" or "God will be angry and punish him severely" (See: [[rc://en/ta/man/translate/figs-metaphor]])
# God will rain it down on him
"God will cause it to rain down on him." Here "rain it down on him" represents causing much punishment to happen to the man. AT: "God will punish him severely" (See: [[rc://en/ta/man/translate/figs-metaphor]])