We are talking past each other because we are focused on slightly different things.
"Fully independent? Nothing is fully independent of the universe it resides in."
Indeed. But there are levels of independence. That is, do the laws of the simulation: 1) merely provide an environment in which there can be turing completeness. or 2) is some aspect of that turing completeness explicit in those laws. Again, redstone(2) vs RNA(1).
And in a similar vain, 3) is the world initialised with some low entropy state and merely lets that run. Or 4) is the simulator constantly randomly generating states?
If you can manage 1 and 3, that would be amazing. Anything less, might still be great, or nothing special. It will really depend on the exact nature of the simulation.
And I would wager that 1 and 3 can only be reached by simulating some sort of entropy flow that causes self-organisation + self-catalysation.
But maybe a much more compute rich universe as you seem to be planning (?) might work. You should surely try if you have ideas. My comments are by no means meant to discourage you!
---
Note that from the perspective of entropy, there are 4 levels of organisation:
a) direct, the structure is the end result of high entropy (for gravity this is globes)
b) indrect, the structure is caused by the flow, but are not the end result (for gravity this is disks, but meandering rivers, crystals or organic molecules are other examples)
c) self-catalysation, (by lack of better term) like indirect, but the structure grows more than linear because more structure creates more structure[1]
d) self-copying, like self-catalysation, but in discrete space/time steps
Somewhere after (c) you would get self selection of the faster/better copiers ... which might lead to what falls squarely in a recognisable definition of life.
[1] https://en.wikipedia.org/wiki/Autocatalytic_set
---
"But its a question of whether life is a product of information and computation, or a product of more specific principles. Who really knows."
That is an interesting saying. What would be more specific principles? And maybe looking at life from the perspective of information and computation is not the most useful?
(That is why I said turing completeness is not so important to focus on, most simulations like we are talking about here are trivially turing complete.)
"Who really knows" :) our universe is surely 1 and 3, and life is at least 3 emergent system steps away from its most fundamental laws.