What should one who earned money from drug dealing during his ignorant past, then embraced Islam, do with this money, and what is the validity of the saying that Allah is Good and accepts only what is good, and therefore it is not permissible to give it away as charity?

It is by the grace and mercy of Allah that Islam demolishes all sins and transgressions that came before it. So, if a disbeliever embraces Islam, Allah forgives them all that they did during their days of disbelief, based on the Almighty's saying: (Say to those who have disbelieved, if they cease, what has passed will be forgiven for them), and the Prophet, peace and blessings be upon him, said to Amr ibn al-Aas: (Have you not known that Islam demolishes what came before it?). Accordingly, money acquired through unlawful means before embracing Islam becomes lawful for the Muslim, with the exception of usurped money, which must be returned to its rightful owner.