What is the ruling on not paying attention to the whispers of lawful and unlawful matters (halal and haram) that cause exhaustion and disruption to daily duties, in order to close the door to Satan, especially when these whispers reach the point of declaring a person an infidel (takfir) for actions unrelated to religion?

Whispers [Waswasah] are among the worst ailments that corrupt one's religion and worldly life. The optimal cure for them is to disregard them and pay no attention to them. This is the healing, not a forbidden medicine. Go on with your life normally and strive against Satan. The default is permissibility and lawfulness, and prohibition is only decreed with evidence. Ask people of knowledge about what is unclear to you, then pay no attention to the whispers. The distress you experience is not a response to Allah's law, but rather from the whispers. Strive in supplication for Allah to remove the whispers from you.