What should a man do who has invested in a private company whose products are halal, but it does not deal with usury, and there is a possibility that it may start dealing with it in the future, and he cannot sell his share except by selling the company or with the consent of another buyer? And what should he do with the profits if he manages to sell his share? And are the profits permissible if the percentage of usury is less than 33%?

There is no harm in you remaining a partner in this company as long as it does not currently engage in usury. Your mere apprehension of their future engagement in usury does not necessitate withdrawal from it unless that actually occurs. If you withdraw after usury has taken place, you are only required to dispose of the illicit profits. There is no sin upon you concerning the fact that the funds of your non-Muslim partners were acquired through usurious loans, because the sin of borrowing with usury falls upon the borrower. It is forbidden to contribute to companies that engage in usury or other forbidden acts, whether frequently or infrequently, because the shareholder is a partner in all of the company's forbidden dealings.