That's kind of a bold statement though. If tidal heating is in your opinion not caused by a gravity differential, you're going far beyond and outside the source

That's kind of a bold statement though. If tidal heating is in your opinion not caused by a gravity differential, you're going far beyond and outside the source you linked to, and I would like to hear what alternative you're proposing. The "conventional" explanation for tidal heating is that a body is being squeezed repeatedly, for which the changing gravity gradient I calculated does seem an appropriate measure. The paper you linked to used eccentricity, whereas I used periapsis and apoapsis - it's the same thing mathematically. Not sure where this "clearly eccentricity is the key" thing comes from when I just told you that Io's orbit is nearly circular. I do like the materials science aspect of the article you linked to in regard to taking rigidity of the body into account, but at a very basic level the problem remains that Io's orbital shape alone doesn't yield enough of a change over time to account for a lot of tidal heating - certainly not compared to Mercury.