Don't take this as an attack of your theory, but rather as simply the recognition of the skeptics' credo that extraordinary claims require extraordinary proof. My interest in your topic is not so much from the theoretical physics side of it as it is from epistemological perspective related to the history of science. Any claim that attempts to falsify the general relativistic model of gravity must be able to withstand a lot of scrutiny if it is to avoid being tossed into the 'crackpot' bin.
(I also have about 20 minutes to kill, and there's nothing good on TV).
That being said, what you are claiming is not entirely new (I'm sure you know but didn't mention -- it's essentially Sakharov's theory of electrogravitation) As you alluded to, Tesla formulated a theory of electrogravitation a century ago (the so-called "hidden" bidirectional EM wave structure in the scalar potential of vaccuum), not to mention that he really anticipated the Aharonov-Bohm effect by over half a century...
The Velikovskian notion that you mentioned (that electromagnetics is the primary force in celestial mechanics, etc.) followed; and that line of thinking culminated in Sakharov (the Soviet 'Feynman') who first formally theorized that gravity (whether classically Newtonian or relativistic curvature of spacetime) is not a fundamental field but is rather a conglomerate of other fields – particularly EM.
Speaking of EM, when you say that "light is the source of all force", there is a bit of anthropocentrism there. Light just happens to be that section of the EM band that our biology happens to utilize for sensory perception... your theory really should be that "electromagnetism is the source of all force".
Sorry for the minor quibble.
Getting back to your theory, I agree with you that (from my understanding) even though the zero point energy in any one mode is minute, that there are so many possible modes of propogation (i.e. frequencies, directions) that in open (i.e.'empty') space the ZPE summed over all possible modes must be enormous (probably greater than nuclear densities as you've implied). So a glass of water won't spontaneously tip over because (by this model) if a trillion ping pong balls are bombarding it from all sides uniformly, it remains stable. (similar in idea to the Obler's Paradox that you mentioned). However, if you could examine it closely enough, those trillions of ping pong balls might be causing that jittery Dirac ZITTERBEWEGUNG that you mentioned.
Anyway, getting back to your idea of harnessing energy from the ZPE, one would think that the effect of the ZPE must be enormous, but it really isn't because of this very uniform density that I just mentioned with the glass of water analogy. (unless you create special conditions where you disturb the uniformity e.g. the Casimir Effect between closely-spaced parallel uncharged plates...)
So in Sakharov's view, gravity could be understood as a variation on the Casimir theme – i.e. caused by background ZPE pressures. In that sense, we are talking about stone-age technology (that is, harnessing gravity as a source of energy... which is really ZPE by proxy, if your theory is correct).
But I say that tongue-in-cheek... I know what you are getting at. In principle there is an enormous reservoir of energy in the empty space all around us. I am just not convinced that we could tap it in the way that you are implying.
So now getting back to the trillion ping pong balls... if Sarkharov's model is correct, if we situate a particle in a sea of EM zero point fluctuations, it should develop a jittery motion, or ZITTERBEWEGUNG. When there are more particles, they are each influenced by not only the background field fluctuations, but also by the ZITTERBEWEGUNG fields of the other particles, and thus the inter-particle coupling due to these fields results in the gravitational force (sort of like a long-range Casimir force). So this view of electrogravitation, because of its electromagnetic underpinning, could be considered as an "already-unified" theory (as it's sometimes referred to in the literature).
There are two things that I like about your theory:
1) -it explains the weakness of the gravity force (you could say that the coupling constant G depends inversely on the (large) high-frequency cutoff of the zero point-fluctuation spectrum)
2) -it explains why there is positive but not negative mass
There is (at least) one thing that I don't like about your theory:
You should be able to shield an electromagnetic force (i.e. particles/ waves) but gravity cannot be shielded.
In contrast, general relativity posits that gravity cannot be shielded because it is a property of spacetime.
Nevertheless, thanks for an interesting topic. At least one that's better than what's on TV.