That being said, my difficultly has been with the concept of everything in existence somehow coming into existence from absolute absence.
You’re not alone, motherengine. This concept, the focus of the scientific discipline of cosmogony
deep and difficult.
There are several explanation for it offered using quantum mechanics. As it’s not possible to test enough of the predictions made by these theories using any equipment yet available (for the most part, these would be vastly larger and more powerful particle colliders) which are wrong can at present only be decided through the formalism of quantum mechanics, which is even more difficult IMHO than overcoming difficulties with the informal concepts into which they can be interpreted.
Starting with these interpretations, we can at least chose favorites that appeal to our intuition and sense of beauty. For me, these are “nothing cosmology” (which should be called “cosmogony”) theories which propose that, in nearly empty, but normal Euclidean space-time universe, over vast time periods, the very low but no zero probability event of a big bang, occurs – or, as Edward Tyron famously (in rarified circles) put it, ca 1970, “the universe is simply one of those things that happens from time to time.” (see this 1994 magazine article
Other theories propose a distinct spacetime event in which space and time appear, before which there are neither. Taking the mention of these and not Tyron and others “nothing” theories in the Wikipedia page for “cosmogony”, I’d say they’re more popular, not in least because celebrity physicist Steven Hawking favors and has work on one.
What all of these theories have in common is that the “nothing” from which “everything” emerges in the big bang is not “absolute”: at least, it contains the fundamental laws of nature, which are not physical objects, but ideas. As accustom as we are to thinking of ideas as being either abstractions of physical phenomena or physical phenomena that occur when human beings think about them, the idea of a universe without much or any matter and energy, or possibly even space and time, that yet contains the fundamental laws of nature that describe the behavior of space, time, matter, and energy, can be mind-boggling. It is, I think, nonetheless implicit in all non-mystical theories of cosmogony (that is, theories not including “god made everything”).