Is the story mentioned about Imam Ahmad al-Rifa'i and his statements that prayer upon the Prophet is better than reciting the Quran, except for Surat al-Kahf, authentic? And what is the ruling on repeating the supplication: "O Allah, bless the Prophet with a prayer by which You save us from the torment of the grave and settle us in Paradise"?

The Imam mentioned might be one of the deviant Sufis. The story of Al-Rifa'i shaking hands with the Prophet, peace and blessings be upon him, is fabricated, and seeing the Prophet, peace and blessings be upon him, while awake after his death is impossible. Preferring prayer upon the Prophet, peace and blessings be upon him, over reciting the Qur'an is not correct; for reciting the Qur'an is better, but preference varies according to the servant's state. The mentioned formula for praying upon the Prophet, peace and blessings be upon him, is permissible, but it is better to stick to the established formulas. One must withdraw from this Imam and not participate in his innovations, while inviting him to the Sunnah with wisdom.