Simulation doesn't mean exact simulation. The value of a continuous property is noise after a certain decimal and can be disregarded for the purposes of simulation. I also believe that 1) is false.

If meat is magical, just build computers out of meat then.

Sure, I agree.

The issue is the word "computer" means not "device we have made" but "universal turing machine".

Ie., a computer is any system which realises a function from the Naturals to the Naturals.

Physics barely, if at all, has any use whatsoever for those functions. It is a very important point.

Computer scientists (ie., discrete mathematicians) are not the people who are even able to describe, engineer and build whatever is needed for an AI -- if, as I claim, continuous dynamical properties are needed.

(As, for example, they are needed by pretty much every system.)

Computer scientists do study computers that use real numbers, for example it's known that such computers can solve all problems in #P in polynomial time. Many other areas of computer science also use plenty of real analysis.

It seems at point 3 that organic plasticity requires features smaller than a Planck length, is that right?

Whatever the length of the smallest discrete unit of spacetime, say, L -- then continuous spatial and temporal properties are those which have a state density O(1/L^2).

This may seem weird, and indeed, it's far less weird if you just say "continuous".

But here's an intuition: spatio-temporal continuity is "scale-free" in the sense that stuff happening at the sub-proton is affected by stuff happening at the galactic.

Thus reality has to be able to "zoom" from the sub-proton to the galactic.

In the case of organic plasticity, I do think that macroscopic effects which are whole-body distributed (including, eg., thoughts) have to drive protein expression at the sub-sub-celluar.

Consider simulating that with a low-state discrete computer: it is many orders of magnitude more data than a planet-sized computer could store and many more years than the lifetime of the universe (consider the number of molecules to store, and their interaction effects from whole-body down).

Running operations at anything in the nanoseconds makes this simulation impossible. It simply does need to be much closer to O(1/L^2).

I don’t think claims 1 or 4 are justified (where claim 4 is interpreted in the relevant sense), and I’m not sure quite what you mean by claim 2.