Dear Dr. Christian Corda,
as explained in my Essay the derivation of General relativity from the more fundamental canonical theory involves the approximation of the total energy-momentum-stress by the energy-momentum-stress for matter alone. If we relax this approximation and maintain the total energy-momentum-stress, then we do not derive the usual Hilbert & Einstein equations but a generalized equation as the equation 94 in the reference 18 in my Essay.
That generalized equation is your equation 2, except by the notation (Tab(EXTRA) corresponds to Tab(c) in your equation 2) and because the physical interpretation of the new energy-momentum-stress tensor term is somehow different.
In your "Conclusion Remarks", you speculate about how the new equation (2) could, in principle, solve the Dark Energy, Dark Matter and Pioneer anomalies.
We already addressed the issue of Dark Energy in page 53 of the same reference 18. Since we have the explicit form for the new energy-momentum-stress tensor, we compute its value and obtained a cosmological constant of order 10-54 (in Standard Units), which is very close to the last observed value of 10-52. This was then interpreted as an important advance, specially since other approaches to the cosmological constant fail by huge errors. The so called biggest mistake ever in physics!
We did a more accurate computation recently and obtained a value of order 10-52 in complete agreement with observation. This has still to be verified by other experts, but it seems that a natural solution to the Dark Energy problem is already at your hand.
Regarding Dark Matter, we are working in this as well. As said in the same reference 18, first research seems to support the idea that the new theory of gravity also solves the Dark Matter problem. We can already explain observational data that cannot be explained neither by GR+DM, nor by other models as MOND, TeVeS, PCG... Moreover, we can combine both the cosmological and the astrophysical models and then solve some other mysteries, such as why the astrophysical constant a0 is numerically close to the Hubble aH. Our new theory predicts a0 = 1/8 aH.
I know that some authors consider that the Pioneer anomaly must be related to Dark Matter, because the scale of the anomalous acceleration are very close. I have not studied the Pioneer anomaly enough and cannot say. However, there many other foundational issues that you cite are solved in our approach.
Regards.
Note:
General readers that cannot access to the reference 18 can see the pages 9 and 10 of the associated Executive summary available online for free download.