Is it permissible for a student on scholarship, who believes his scholarship is unlawful, to receive the stipend for his two remaining months solely to pay off an old debt?

You must refer to the competent authority to know the conditions for deserving the scholarship and allowances, and whether all conditions must be met. If your scholarship is approved despite some conditions not being met, you should communicate with the authority and inform them of the truth. If they order you to stop, you must cease receiving the allowance and absolve yourself of what was previously taken, for the Prophet, peace and blessings be upon him, said: "Muslims are bound by their conditions." If the competent authority approves the scholarship, then you are permitted to continue and benefit from the allowance.