What is the ruling on wishing for death out of fear of losing one's faith and falling into disbelief, or wishing for it to avoid witnessing the death of one's family?

It is not permissible to wish for death merely out of fear of a relative's death. However, it is permissible to fear tribulation (fitnah) in one's religion. The permissibility of this is indicated in the Qur'an and the Sunnah. Mary (peace be upon her) wished for death out of fear that evil would be thought of her in her religion, or that her people would be shamed by it, or that they would fall into slander because of her. The Prophet (peace be upon him) supplicated for death out of fear of tribulation in religion. Therefore, there is no harm for a righteous servant to wish for death if they fear for their religion, and this does not fall under the prohibition mentioned in the hadith. If one fears harm to their religion or tribulation therein, then there is no dislike for it. Many of the Salaf (early Muslims) did this when they feared tribulation in their religion, among them were Umar ibn al-Khattab and Abis al-Ghifari.