Should I stop this work to force my colleague to leave it, knowing that he relies on his income from it, and that he contributed to my obtaining it, and the company is efficiently receiving the work?

The impermissibility of the previous action was based on violating the terms of the contract with the company. You can inform the company about the matter. If they agree to the current arrangement between you and your colleague, then there is no objection. Otherwise, it is not permissible for either of you to continue this situation, which violates the company's terms. You must either end the division of work between you or cease it altogether. Repaying kindness and favors should not come at the expense of others. You can repay your colleague's kindness by helping him find another job and supporting him financially, while supplicating for ease in his affairs.