What is the ruling on dealing with a father who curses, reviles, and damns his children for the most trivial reasons, weakens their personalities, causes them to lose the respect of society, leads to their children (his grandchildren) not respecting them, in addition to smoking inside the house in front of everyone?

One must be keen on honoring their parents and being patient with them, and respond to their ill-treatment with kindness, as Allah Almighty says: "Nor can goodness and evil be equal. Repel (evil) with what is better: then will he between whom and thee was hatred become as it were thy friend and intimate! And no one will be granted such goodness except those who exercise patience, and no one will be granted such goodness except the owner of the great portion (of happiness in the Hereafter). And if an evil suggestion comes to you from Satan, then seek refuge in Allah. Indeed, He is the All-Hearer, the All-Knower." And persist in the prescribed remembrances (adhkar) and incantations for protection from the father's injustice, and the children must respect you and not be affected by the father's treatment.