How can one verify the truth of a claim of sorcery, and what should be done now that a legitimate engagement has taken place?

One must repent to Allah Almighty from the forbidden relationship outside the bounds of marriage. The growing love for one's wife may be natural and not magic. One must beware of charlatans who stir up disputes between spouses. If magic is present, it can be treated with Ruqyah Shariah (Islamic exorcism), and the wife should be advised to repent if she was the cause.