Was the husband's concealment of his non-virgin wife—from whom he had children—right or wrong? And will he be rewarded for it with a good deed or a bad deed?

May Allah reward you for concealing the Muslim woman's (secret). We draw your attention to the fact that the loss of virginity can be due to multiple reasons. Therefore, do not think ill of her unless she admits it or you find conclusive evidence, because the default for Muslim women is chastity. Accusing chaste women without evidence necessitates the punishment for slander, and (earns) cursing and a great torment, and it is one of the seven destructive sins. You should not ask your wife about the reason for the loss of her virginity. Rather, have a good opinion of her and cut off any doubts, which may come from Satan.