Does the third verse of Surat An-Nur apply to a man who has never committed adultery and married an adulterous woman, knowing that she is pregnant by him? Is what happened considered a divine punishment? What is the fate of the child? Should he continue to financially support her? What is the appropriate advice in this situation?

You erred in painstakingly delving into your wife's past and questioning her about a previous illicit relationship. Had you feared Allah, she would have remained in good health. She is not obligated to confess; rather, it is her duty to conceal herself and repent. The verse "The fornicator does not marry except a fornicator or a polytheist" does not apply to you. Marriage to a fornicatress is a matter of scholarly disagreement, but it proceeds if it has been concluded. If the woman gives birth six months after the marriage contract, the child is yours, unless there is a li'an (oath of condemnation). Entering a church to observe Christian rituals is an abominable act, and participation is even more severe and can amount to disbelief (kufr), but it does not necessarily mean that one who commits an act of kufr becomes a disbeliever. It is obligatory to advise the woman. If she repents and becomes righteous, then keep her. If she persists (in her sin), then separate from her, and the marriage becomes nullified by her apostasy. Take your time in choosing a wife and seek Allah's guidance (istikharah).