Is the "Salat al-Fatih" considered a form of invoking blessings upon the Prophet Muhammad (peace and blessings be upon him), and what is the ruling on one who abandons it after having recited it?

The Tijaniyya tariqa is an innovation (bid'ah) and it is not permissible to follow it. One must adhere to what the Messenger of Allah, peace and blessings be upon him, brought, as Allah Almighty says: "Say, [O Muhammad], 'If you should love Allah, then follow me, [so] Allah will love you and forgive you your sins.'" (Al Imran/31), and other verses that command following the Shari'ah and forbid innovations. Salat al-Fatih was not reported from the Prophet, peace and blessings be upon him. The correct forms of sending blessings upon him are those he taught to his companions, such as: "O Allah, send prayers upon Muhammad and upon the family of Muhammad, as You sent prayers upon Ibrahim and the family of Ibrahim, You are indeed Worthy of Praise, Full of Glory. O Allah, send blessings upon Muhammad and upon the family of Muhammad, as You sent blessings upon Ibrahim and the family of Ibrahim, You are indeed Worthy of Praise, Full of Glory."