Is what happens to us during sleep—the body tossing and turning every 7 minutes, the expulsion of thick saliva, the purification of memory through dreams, salvation from the viral encephalitis of sleep and panic attacks, and not being afflicted with sleep paralysis—from Allah's kindness to us, and is this matter valid?

Sleep is a blessing and a sign from among the signs of Allah. Allah Almighty has mentioned it in the Quran. There is nothing, neither Islamically nor customarily, that prevents one from moving or turning a sleeping person, and this might not be every seven minutes. As for the supplication, "O Allah, I have laid down my side," it is agreed upon, but the addition "O Allah, have mercy on us with Your mercy" is not part of it. You may consult the medical consultations section of the website to benefit from the scientific aspects mentioned in the question.