: If you are talking in purely physical terms, then 'wealth' (i.e. mineral and vegetable resource) has remained roughly constant since humanity's start;
Its not wealth then, its just material.
Wealth is "objects of human desire" (websters, 1913) - in other words its a broad philosophical term describing the sum of the usefulness of an item (or intangible) to a person or persons.
: To speak in terms of 'wealth creation' is merely describing the 'talking up' of value; it's not the physical act of creating more resources; which is impossible in a closed system like Earth.
Its the act of transforming something which people do not find useful (tonnes of iron ore and coal) into something they do find use for (iron, then cars etc etc etc). That process is wealth creation.
: merely that you've converted the existing arrangement to suit your own needs more.
Here's a few tonnes of random material from our planet - you try and turn it into something useful - its not poker, and no amount of 'talking up' will change it into a car, plow or PC.
: In thermodynamic terms; in physical terms, the Earth is very definitely a zero-sum-gain system;
This is unconnected to the term or concept of wealth. I would rather live on a planet with 50% loss of material but with things which enhanced my survivability than on some 'pure' world whose contents were untouched, and useless for life.
Don't mix concepts.