Is it obligatory for my husband's brother to leave his job at the interest-based bank due to his suffering from psychological depression, and what is the ruling on gifts and what we eat in his house?

Your husband's brother must leave his job if it involves helping with usury, whether he suffers from depression or not, because Allah Almighty says: "And do not cooperate in sin and aggression," and because the Prophet, peace and blessings be upon him, "cursed the one who consumes usury, the one who feeds it, its scribe, and its two witnesses, and he said: 'They are all equal.'"