The mass of helium is 4.002602 g/mol. Divide by Avogdro's number, and a single atom of helium weighs 6.646E-24 g. The difference in mass is what powers the sun. Parent is simply making the same argument on the scale of a proton split into its parts.
(disclaimer: I know, blabla deuterium, not protons and neutrons. However, see the definition of a state function.)
He holds the liquid gold at 1127C. It would take an approximate pressure of 2.1 * 10^-7 atm for liquid gold to boil at 1127C. Now, it strikes me as very unlikely that he is using a close-to-perfect vacuum for this, especially since running any vacuum at all will encourage evaporation, but without further data, who knows, right?
Always draw your curves, then plot your reading.