Alan,
I don't think it is wise to develop an theory that doesn't have an explanation for its motive force [or for the corrections it predicts], that would put us back to Newtonian gravity with no explanation for its mechanics.
GR obviously attempts to overcome this by giving us the correct answer but couches the answer as being the result of 'space-time' geometry [but it also fails to address how gravity works - undetected 'gravitons and g-waves included]
Tetryonics explains the quantum interactions for Newtonian Gravity and GR through GEM interactions accounting for both theories and paving the way for testable refinements to the nett force of Gravitation.
BUT [and it is a bit BUT], any test using EM waves must accurately calculate the exact interactions these fields have on top of the gravity field [unless you can exclude them]....and that's where Newton and Einstein both failed [they had no explanation of the quantum interactions at play that give rise the nett force of gravitation] because they never differentiated between EM mass and Matter.
In short, call it what you want but you need a solid mechanical basis on which to explain established proven theories so it can be mathematically modelled and physically tested in some way [otherwise it remains a speculative theory like strings etc].
Re: the effect Venus had on Mercury's orbital perturbations - any change in either planet's EM field would have an effect, but no where near as significant as the SUN's GEM effect on Mercury by many orders of magnitude given the relative distances between each of them [G&E fields are inverse squared and dipole M-fields are inverse cubed].
Again it would require the modelling of various the theories against observational data [and if that data is generated from EM waves...well I think you get the point]
Given the GEM interactions and the geometry of the fields I am more than confident that the SUN's M-field is the source of Mercury's orbital precession and that close flybys of spacecraft in Earth's GEM fields will bear it out [but an accurate field model of the quantum GEM interactions is required to prove this and this is beyond my resources at present].