Clarifying this issue is too difficult and would, in my opinion, lead too far. Please, I think, let us confine ourselves to the following statement, which I mean seriously: physics does not know what an inert mass is. I accept that mass points are of size 0 and near 0 mass. All known mass (the mass of an iron ball) is the mass of the quarks in the nucleus of the atom un. the only known masses are those of the relativistic masses of the quarks in the nucleus. Also, the proton figure shown shows 3 quarks orbiting at the speed of light, with mass growth giving nearly 70% of the mass of the proton, the rest being the ether sea and gluons. I seem to remember pointing you to the extended article with its URL link.