Art by smbc-comics
Consciousness is often said to disappear in deep, dreamless sleep. We argue that this assumption is oversimplified. Unless dreamless sleep is defined as unconscious from the outset there are good empirical and theoretical reasons for saying that a range of different types of sleep experience, some of which are distinct from dreaming, can occur in all stages of sleep.
Pubmed Articles
Does Consciousness Disappear in Dreamless Sleep?
Sciencealert Article We Were Wrong About Consciousness Disappearing in Dreamless Sleep, Say Scientists
This reasoning goes all the way back to Epicurus. With regard to your latter points, Epicurus thought they were also solved by being dead. For someone to miss out on something, they have to exist in the first place. No person, no missing out. And for not existing to be bad, a person must be around to be upset about it.