Is the money remaining from a previous relationship, which was sent to me by a man who does not wish to reclaim it, considered unlawful (haram)? And is what was purchased with this money, such as clothing, considered unlawful (haram)? And what should I do with the remaining money?

You have done well in severing unlawful ties, and we ask Allah to accept your repentance. Money acquired as an illicit, unreciprocated gift is permissible to use. However, if it was acquired through an illicit exchange, it must be disposed of by spending it on the welfare of Muslims or giving it to the poor, and it is not permissible to return it to its owner. What you have spent from it only necessitates repentance.