> On the most trivial level, we can infer the mass and charge of a particle from its gravitational field.
How does gravity tell you the charge of a particle? I didn't even know it carries information about the sign of the charge, let alone the magnitude.
Also, the reference to “known links between the solutions of Yang-Mills theory and those of gravity” (Y-M equations describing charge and EM field) seems to speculatively imply that charge-related information is encoded in the geometry of spacetime, alongside gravitational effects
Perhaps you can just assume a radius where the electron self-repulsion energy equals its own mass, by m = E/(c^2).