Is it permissible to seek forgiveness using the formula: "I seek forgiveness from Allah according to the number of His creation, the measure of His own pleasure, the weight of His Throne, and the extent of His words"? And would its reward be greater than that of ordinary seeking of forgiveness?

There is no objection to using the wording mentioned in the question, although it is preferable to stick to the ma'thur (traditionally transmitted) forms of seeking forgiveness, such as Sayyid al-Istighfar or "Astaghfirullah" (I seek forgiveness from Allah). The difference in reward between these forms is a matter of the unseen (ghayb), but the reward for the ma'thur forms has been established. Therefore, it is better to limit oneself to what has been authentically transmitted from the Prophet, peace and blessings be upon him, regarding adhkar (remembrances).