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
I'm genuinely surprised that the idea that something bad might happen to you when you're dead or that it could be painful etc is anywhere near as prevalent as it is. To me, that makes absolutely no sense. Of course dying might be painful... But death? Once you brain no longer works? Feels obvious to me that you won't feel, well, anything. The thing that frightens me about death wouldn't be the experience of being dead, but rather not being able to do any more things and not existing anymore.
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.