The difficulty is to separate speculations from facts. Clearly the spacetime fabric fills those portions of three dimensional volume which are unoccupied by what we perceive as matter.When you consider how ordinary matter moves through the sea of the spacetime fabric, you can see how it creates inertia (resistance to acceleration), since you have to push against it to start it flowing around your fundamental particles and into the void you leave behind you.The major problem with the idea of spacetime fabric as a fluid is the speed of gravity, which is light speed. It is interesting that Hawking's radiation formula for black holes suggests that the effective temperature of the black hole (for emission of black body radiation) is inversely proportional to the mass of the black hole.If fundamental particles are effectively black holes, they would emit Hawking radiation with energy far above ordinary gamma rays. This would mean that they would not interact very much with electrons, just with nuclei (or the Higgs field around the fundamental particles in nuclei).The main way these extremely high gamma rays would be detected in large quantitied would be by the momentum they impart as they are stopped by Higgs bosons in nuclei. Thus, gravity.The statistical spread of these gamma rays (black body radiation spectrum) would ensure that a few are high above average energy. The random impacts of particularly high energy impacts would provide a causual trigger mechanism for radioactivity. However, the rigorous mathematical treatment of nuclear physics is an unappealing project.One problem is that the assumptions used to derive the Hawking radiation formula are not regarded as being valid for very small masses like fundamental particles.