What is the ruling on the imam's saying in the Fajr Qunut, "Our evil ascends to You, and Your good descends to us, so do not hold us accountable," and what is the ruling on the prayer if the supplication includes words not from it?

There is no objection to supplicating with non-prescribed (non-Qur'anic or non-Prophetic) supplications, both inside and outside of prayer, as long as the supplication does not involve sin or severance of kinship ties. This is supported by what Al-Bukhari and Muslim narrated from Ibn Mas'ud that the Prophet, peace and blessings be upon him, said after the Tashahhud (definition): "Then let him choose of the supplication what he likes most, and supplicate." This indicates the permissibility of supplicating in prayer with words not found in the Qur'an, and this is the opinion of the majority of scholars. Scholars have also differed on whether it is permissible to supplicate in prayer specifically for worldly needs, and the preponderant opinion is that it is permissible. Ibn Hajar supported this by stating that the hadith (definition) indicates the permissibility of supplicating in prayer with what the worshiper chooses from matters of this world and the Hereafter. Similarly, Ibn 'Uthaymeen mentioned that the Messenger of Allah, peace and blessings be upon him, said: "Let one of you ask his Lord for everything, even for the strap of his sandal," and that the phrase "what he wishes" implies generality. In conclusion, there is no objection to supplicating with non-prescribed supplications in prayer, but it is better to supplicate with the prescribed supplications.