How can one reconcile the prohibition of cursing, given that it is not among the manners of a monotheist, with the Messenger’s cursing of Jews and Christians in general, and his specifically cursing certain individuals then supplicating for them? Are there any regulations for cursing specific individuals?

It is permissible to curse disbelievers and those Muslims whose transgression has been established. The cursing should be general, not specific, except for those whose death in disbelief is known, such as Pharaoh and Haman. As for the Prophet's (peace and blessings be upon him) cursing of certain specified individuals, this is one of his unique prerogatives. If the one cursed was not deserving, that cursing would become a purification and a reward for him on the Day of Judgment.