Should I forgive my husband who molested my ten-year-old niece three times without deflowering her, especially since he has shown remorse, and given that he treats me with kindness and we have three children?

If the husband is remorseful for the sin and has become upright, then the wife should not seek divorce. Rather, she should live with him kindly, conceal his past, and be an aid to him in obedience, for repentance erases what came before it.