What should the couple do about recurring fights that escalate to the point of the wife hitting, knowing that the husband is stronger and is not harmed, and they are generally happy?

Dealing with a wife's violence requires understanding its cause and addressing it. The violence might stem from a bad childhood, the husband's weak personality, or the wife being influenced by stories of violence. The husband should remind his wife of his rights and her duties, the punishment for assaulting him, and that her actions will affect the children's upbringing. If these methods fail, then it is permissible to use sternness in words, abandonment (boycotting the bed), or a non-injurious beating, to affirm his guardianship (qawamah) and reform the wife. This unhealthy situation must be rectified, especially given the presence of children.