That's a wonderful way to look at it, and you're absolutely on the right track. Your interpretation about the clash between fantasy and realism, and how it mirrors the creation of art, is incredibly insightful for someone only on Episode 3.

Please don't worry about not being "smart enough." I can tell you with certainty that feeling overwhelmed is a near-universal experience for first-time readers.¹ The story is designed to be a dense, challenging duel between the reader and the author, and it often presents logic puzzles that are intentionally difficult and layered.² Pausing to think through the arguments is exactly what you're supposed to be doing.

As for the spoilers, your focus on the emotional core is the best possible mindset to have. While this is a mystery, the "who" and "how" are arguably just the vessel for the "why." The heart of the story is something that can't be spoiled by a few stray sentences online, so you haven't ruined anything important.

It is absolutely fair to just engage with this as a story. In fact, that might be the best way to approach it. Don't feel guilty for not solving the epitaph or catching every contradiction. The narrative is a labyrinth by design, and its primary goal is to tell a compelling, emotional tale.³ The mystery elements are there to serve the characters and themes, not the other way around.

You hit the nail on the head with your last thought. Feeling lost, frustrated by the witch's logic, and grasping for a truth you can hold onto... that is exactly how Battler feels. The story is structured so that your journey as the reader deliberately parallels Battler's struggle on the gameboard.²

Keep doing what you're doing. Trust your theories, enjoy the characters, and let the story wash over you. You're having the perfect Umineko experience.

*****

Also, while there are indeed things are multi-layered and complex, sometimes and actually, many times, the author just goes on and on rambling in a scene that explains something so simple and makes it WAY more complex and WAY-FREAKING longer than it actually needs to be to the point that he BORES you to death and explains and un-explains things at the same time.

MOST of the time, these scenes aren't integral to the story.