I do not accept that reality is the set of all things that exist.
To me, this seems like you're equivocating the objects in the set with the very concept of the set itself. I don't think it's illogical to make a distinction between those.
You are missing some steps here. Most sets are not both the subset and the powerset of itself. In fact, that is ordinarily counter to set theory.
It sounds to me like you're adopting the language of Christopher Langan, but Langan has been criticized by mathematicians on a number of occasions precisely due to his misuse of set theory in his arguments for CTMU.
Langan frequently uses technical language in idiosyncratic ways, which means his writings are outright false on the face of them but, once you dig deeper, they're fractally wrong because his persuasive definitions rely heavily on equivocating unrelated concepts between different fields of study.
Don't listen to the guy. He's fallen into what's known as the "intelligence trap." He's too emotionally committed to recognize the errors in his logic, but you might not be yet. Treat him as a cautionary tale. You're smarter than this.
"Reality" and "exists" are not interchangeable. One is a noun and the other is a verb. "Reality" and "existence" are also not quite interchangeable. Fictional narratives and simulations exist, but they are not real. Likewise, the past is real, but it does not exist.
Neither are "material" and "physical" interchangeable. Gravity is physical, but it is immaterial, for example. Concepts emerge from material neuronal activity, but they themselves are usually treated as non-physical.
I might accept "physical" and "real" as synonyms, though.
That sounds like the Ganzfeld Effect. It's been used by mystics for thousands of years to have supposed dialogues with spirits. I have a tome of ancient Greco-Roman Necromancy that uses the same trick to summon shades of the dead in dimly lit caves.
If you're suggestible, sleep deprived, and hungry, then the effect can be quite dramatic. Summonings in grimoiric tradition often advised fasting and an entire night of prayer before evoking spirits for this reason. Mages figured out that it could reliably produce mystical experiences and believed it was a form of magic.
It's not. It's just a way of tricking the pattern-recognition part of our brains.
Did God speak to you? That would be a more interesting point of discussion. And I don't mean speaking to you in your head as a mental voice, because that's fairly easy to trigger. The tulpa community and many chaos magick practices with thoughtforms have that down to almost a science now. I mean, did God make audible noise that you heard with your ears?
If not, then your experience means basically nothing.
Oh wow, I was right about Langan. I hadn't read this part yet when I wrote my earlier response. I was going to get all of my ideas out as they came to me and then revise them after re-reading your post in full.
I guess that entire portion of my reply can remain intact, then. Suffice to say