These are weird conclusions. Any attempt to measure “reality” gives some amount of uncertainty. The only way for this to lead to the relatively stable experience you perceive is if those small variations in measurement lead to relatively small differences in perception. In which case, you can truncate the resolution of your simulation and still get plausible results.

I assure you there are plenty of groups out there simulating systems that operate with similar densities (but lower volume) to the brain.