Is it permissible to supplicate that one who has wronged me realize the extent of their wrongdoing, regret it, and come to apologize? And will Allah hold them accountable for that?

You have done well by repenting from this relationship. From the sincerity of repentance is to avoid the causes of sin, cut off the paths leading to it, and beware of being lured by Satan. Remain steadfast in your repentance and do not preoccupy yourself with this young man. If he harms you, forgive him and pardon him; there is no need for his apology. Occupy yourself with what benefits you and brings you closer to your Lord, and ask Allah to grant you a righteous husband.