Hi Peter,
I'm not sure whether you believe low velocity motion creates fermions, or whether you're assuming the existence of fermions everywhere, so it's kind of hard to respond to your first point.
Local gravity is not designed to "help acceptability"; it either serves as the medium for electromagnetic propagation or not. Since gravity exists everywhere, it clearly is available to serve this function. And since it deflects light, it is not just an inert presence. My opinion is that the fermion and plasma aspects you focus on are not relevant to my essay, and if you wish to reframe everything in your own conceptual terms, you will probably miss the point.
In answer to your questions:
1. If fermions absorb and reemit EM energy in reality, then this will happen whenever fermions are present. Fermions are not assumed to be present in the gravitational field in question.
2. Light emitted at any point will travel with speed c in the local gravity, independent of the speed of the "center of mass rest frame" (unless it is the center of mass that is the dominant source of gravity.) If the frame you are interested in is moving with velocity v in the local gravitational field, then the relative velocity will be v c. Einstein imagined that c is attached to every moving reference frame. This was an invention of his that solved his immediate problem while destroying our intuitive notions of time.
Why not have another beer?
Best regards,
Edwin Eugene Klingman