Reality is probabilistic and none knows why, almost like someone programmed a video game.

How is that anything like a video game? What even is your reasoning here?

You get what I’m saying - just by me looking at the experiment result changes. I have to observe the reality in order to force it’s hand and render the outcome.

According to some interpretations, but none of the main ones. And it would in no way imply simulation even if it was true.

If I were to design a video game I would surely not render the entire world unless someone interacts with it - to conserve resources.

Having every possibility simulated until observed would be infinitely more resources intensive than just having a classical single state the whole time. Which is why actual video game designers don’t do this.

And now there is this: modern work suggests that the extra spatial dimension itself may emerge from quantum entanglement. Roughly: 2D quantum information → entanglement structure → emergent 3D geometry/spacetime.

No it doesn’t. I’m guessing that this is some vague misunderstood conception of the holographic principle but this is not how it works

And why is spacetime quantized? - This is pretty crazy imo.

It’s not. Spacetime is not quantized in QM