Doug Benscoter: Atomism and Its Irrelevance to Classical Theism -- "Peter van Inwagen, for instance, holds to mereological nihilism: that no composite material thing really exists. He does, nevertheless, make an exception for living things."
While I hadn't yet thought of it in terms of "composite material thing[s]", and of course (being just a normal non-academic person ... like you), I had never encountered the term 'mereological nihilism', I had years ago reached the conclusion that almost none of the (supposed) entities we speak of do actually exist, but that living entities do exist. That is, the sun and moon and stars, and the earth, do not really exist. But you really do exist, and the individual cells comprising your body really do exist.
I had come to these conclusions in considering the 'Perseus' Ship Paradox', which is the paradox of identity. I had concluded that only things inherently possessing identity really exist. And the only material entities possessing inherent identity of which I am aware are living things. Perhaps sub-atomic particles also possess some sort of inherent identity, though I can't see it including "selfness", which seems to me the key thing in identity.