E=mc^2 --> m=E/c^2

We may be confusing constants and variables. C is probably a constant: so much so that Feynman eliminated C from his path integrals to make them simpler. Feynman always said that he would put C back into his equations if necessary but he never had to do this (as far as I know).

You say that E and m are both constants. They are in fact variables: one of them is the dependent variable and the other is the independent variable, depending on how you look at them. They may indeed be infinitely variable but I cannot be certain about this because I am no good with infinities.

You say that the Planck constant is not a true constant because it increases with time. If the Planck constant increases with time then it must be a variable; it varies (as you say) with respect to time. Or perhaps it is an untrue constant or even a partial variable?

I do not understand your definition of rest mass. Perhaps it would help if we contrasted rest mass with active mass.

As you know, mass is related to gravity. But it is the active mass that is the source of gravity and this active mass is not simply the same as (or proportional to) the energy, as implied by E=mc^2.

Active mass is the energy density plus the sum of pressures and this is what causes the inward acceleration of gravity.

Given this simple definition of active mass, how would you now define rest mass (which is even simpler)?

Here is a clue: the definition of rest mass does not involve entropy or negentropy or posentropy (as far as I know).

Use simple mathematics to explain your proposition, if it helps.