Is the money ruled as compensation for an accident that befell my brother, caused by a touch from the jinn, lawful or unlawful?

There is no objection to taking the money awarded by the court as "arsh" (blood money/compensation) for an unintentional offense, for the Prophet, peace and blessings be upon him, said: "For every unintentional error there is compensation." And your brother's affliction with jinn possession does not waive his right to compensation, nor does it absolve the facility owner of responsibility if he did not take safety precautions.