Is trading in the stock market with shares of usurious banks unlawful, and what should be done with the money earned from it, especially given that a portion has already been spent?

It is not permissible to buy shares in usurious banks, due to the prohibition of their activity based on usury, and because buying their shares is considered assisting them in their continuation. Allah Almighty says: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression." If you bought these shares out of ignorance of the ruling, then you must annul the contract, return the shares, reclaim your money, and dispose of the profits by spending them on charitable causes, as Allah Almighty says: "O you who have believed, fear Allah and give up what remains [due to you] of interest, if you should be believers." If you cannot annul the contract now, you are not permitted to sell them. You must continue to dispose of the unlawful money each year. There is no blame upon you for what you spent of profits previously due to your ignorance of the ruling.