Is the wife's statement, "Do not make me curse marriage," considered an act of disbelief (kufr) if she does not intend it, and is she held accountable for it on the basis of "intending to curse a part of Allah's law"? And what is the ruling on intending to commit an act of disbelief without actually carrying it out?

A wife's statement, "Don't make me curse the marriage," is impermissible because it is a threat to commit a sin, and she must repent. This statement does not result in disbelief (kufr) because it appears she intended to curse their specific marital relationship, not to curse Allah's law. Both spouses must avoid the causes of discord. A Muslim is required to guard their tongue and be wary of its slips, for the tongue is one of the most dangerous limbs.