How is it possible to deal with a father who is influenced by his second wife and accuses his children of disobedience, and is his insistence on his stance considered disobedience on his part?

It is advisable to avoid, as much as possible, anything that provokes the stepmother's anger, to be kind to her, to endure her harm with patience, and to repel her evil with good, seeking reward from Allah, in accordance with the Almighty's saying: "And not equal are the good deed and the bad. Repel [evil] with that which is better, and thereupon the one whom between you and him is enmity [will become] as though he was a devoted friend. But none is granted it except those who are patient, and none is granted it except one having a great share [of good]." If you do that, then there is no blame upon you thereafter, and you will not be held accountable for your father's displeasure.