Honesty and Promises

• Is saying "I will kill you, kill you" in jest to one's sister, with an inner feeling that the intention was not to mock the Qur'an, considered disbelief (kufr) or mockery of the religion, and what should be done about this obsessive whisper (waswas)?
• Is it permissible to secretly marry a married man who refuses to inform his first wife of the marriage and stipulates that the second wife reside in another country far away from him?
• How should one deal with a fiancée who tells her fiancé that she is attracted to someone else, despite their impending marriage, and what is the Islamic guidance in such a case?
• What is the ruling on adopting the view of a trusted authority that a moderate Muslim is better than an extremist Muslim, and that a Muslim with good morals is better than one characterized by the opposite qualities? And does one commit an act of disbelief and sin if they prefer some peaceful disbelievers over oppressive, warring Muslims, or over some Muslims who impose strict interpretations?
• Is it permissible for a Muslim to describe some disbelievers as being of better character than some Muslims?