If you read the quote carefully you will find that it is incompatible with the position you are attributing to Deutsch. For example, he writes about 

levels of universality between AI and ‘universal explainer/constructor’,

which would hardly be necessary if computational universality was equivalent to universal explainer.

The quotes aren't about Turing completeness. What you wrote is irrelevant to the quoted material.

We can't simulate things of which we currently have no understanding. But if at some point in the future we know how to write AGIs, then we would be able to simulate them. And if we don't know how to write AGIs then they won't exist. So if we can write AGIs in the future then memory capacity and processor speed won't impose a limit on our understanding. Any such limit would have to come from some other factor. So is there such a limit and where would it come from?

You said earlier:

But not all inductivists believe in a version of inductivism that supposedly generates theories or scientific knowledge.

What is the version of inductivism that generates no theories or scientific knowledge and what does it accomplish?

But not all inductivists believe in a version of inductivism that supposedly generates theories or scientific knowledge.

That version of inductivism isn't in Li and Vitanyi who haven't even stated the problem described by critics of inductivism. Where is it?

I have corrected the spelling of Vitanyi.

Science is not based on faith, nor on anything else. Scientific knowledge is created by conjecture and criticism. See Chapter I of "Realism and the Aim of Science" by Karl Popper.