Is it permissible to recite the aforementioned litany that begins with "In the name of Allah, Most Gracious, Most Merciful, the Light of Allah has shone, and the Word of Allah has appeared..." and ends with "And may Allah's peace and blessings be upon our Master Muhammad and upon his family and companions"?

Supplications are permissible at any time and in an unlimited number, but it is preferable to restrict oneself to the supplications authentically reported from the Prophet, peace and blessings be upon him, because, as Qadi Iyad said, they combine knowledge of Tawhid (Oneness of God), language, and sincere advice for the Ummah.