One should never under-estimate the contributions of those looking at a problem from a novel perspective. A lot of breakthrough science comes from someone in one discipline coming into a new discipline and seeing it in a new way. That said, your proposals unfortunately don’t take into account some important elements. The first is that relativistic effects are already included in the calculations pertaining to galactic rotational forces and are simply so tiny as to be irrelevant to the central phenomenon. The second is that the CMB shows the visible universe is nearly constant across all scales and therefore the idea of an “oil and water” universe is inconsistent with all observations to date. Furthermore, no data of any kind even remotely implies that ultra-large-scale phenomenon (the problem of why galaxies don’t fly apart) can be attributed to ultra-small-scale behaviors such as tiny deviations in vacuum energy somehow manifesting across enormous swathes of space-time. While analogies can sometimes be useful in helping to explain a phenomenon, they are less often useful as guides to understanding complex phenomenon. This would appear to be the case with regards to your analogy regarding immiscible liquids. So, a good thought-provoking article but unfortunately based upon a less complete understanding of the problem domain than is presently the case.