How can we help a father who is going through a difficult phase and thinking of converting to Christianity, claiming that Islam has been distorted by some and that Muslims do not fully practice it, knowing that he does not allow discussion of this topic?

It is recommended to supplicate for the father for guidance and insight. The claim that the religion of Islam has been distorted is false; for the Quran and Sunnah are preserved by Allah Almighty's protection. The Sunnah is included in the preservation of the Dhikr (remembrance), or its preservation is obligatory to complete the preservation of the Quran. Islam is not to be judged by the state of deviant Muslims, for every soul is held in pledge for what it earns. It is suggested to increase kindness and dutifulness towards the father, and to seek assistance from people of wisdom to clarify the truth to him and the danger of apostasy.