Can I use a source follower to read the floating gate voltage then add a fixed tunneling voltage, then feed it back to the tunneling electrode?
I am familiar with the work by Ohmi, but not specifically this paper.   When I make floating gates, tunneling makes the node positive, and injection makes the node negative.  Ohmi generally used tunneling for both directions.

You can read Dr. Hasler's thesis from Caltech under Carver Mead for the details in chapter two, but the here is a summary:

Simulation model for floating gate