This paper proposes a new definition of the Newtonian/ universal gravitational constant (aka “big G”) which is stated to be very plausibly not a true constant, but only a composite quasi-constant depending on a slightly variable speed of gravity (which is stated to be very close to the speed of light in vacuum [c] defined as the maximum speed limit of any elementary particle allowed in our universe), to which big G is directly proportional) and a very high energetic/massic linear density of vacuum produced by evanescent/off shell virtual particle-antiparticle pairs (to which G is inversely-proportional): this redefinition brings a natural solution of integrating speed of gravity in the big G scalar. This paper also proposes a variable (energy/length scale-dependent) electro-gravitational resistivity of vacuum (EGRV) determining both a variable (energy/length scale-dependent) quantum big G and the known running coupling constant of the electromagnetic field. In conclusion, this article offers a "patch" for Einstein's General relativity (EGR), Newtonian gravitational theory (NGT) and quantum gravity theory (QGT) which all use the classical empirical big G as a kind of gravitational coupling constant in their equations. This paper continues (from alternative angles of view!) the work of other past articles/preprints of the same author.