Is an obligatory act in Ramadan rewarded seventyfold, and a supererogatory act with the reward of an obligatory act?

A lengthy hadith (definition) has been narrated concerning the virtues of the month of Ramadan (definition), mentioning that the month is great and blessed, and that Laylat al-Qadr (the Night of Decree) within it is better than a thousand months. Allah has made its fasting an obligation and its night prayers voluntary. Whoever draws near (to Allah) during it with a good deed is like one who has performed an obligatory act at other times, and whoever performs an obligatory act during it is like one who has performed seventy obligatory acts.

A group of scholars have deemed this hadith weak, and the evidence for this is Ibn Khuzaymah's categorization of it by saying: "Chapter on the virtues of the month of Ramadan, if the report is authentic." Some scholars have found solace in this hadith to argue for the multiplication of rewards for deeds, but what is certain is that obedience in Ramadan has a special virtue and a multiplied reward. However, this specific quantification of multiplication has not been authentically reported from the Prophet, peace and blessings be upon him.