I think you are on the right track. Independent estimates of the size and mass of our universe place it entirely within its own Schwartzschild radius, where the radial dimension and time switch roles due to a sign change in the metric. My theory is therefore that we are in a humongous Black Hole, and that the inexorable chute towards the central singulaity is the inexorable passage of time, while the unbounded outside time dimension becomes unbounded space inside. An interetsing consequence is that "where" quesions and "when" questions have to be interchanged. So the answer to "Where is the event horizon?" is "13.5 billion years ago", and the answer to "What came before the Big Bang" is "The Outside".
Thus I equate the instant of the Big Bang with the event horizon, "seen" from the inside. From that instant, everything evolved more or less as we know it.
I have done the math and the interior universe is one that exhibts an initial infinite rate of expansion, falling to 70Km/s/Mpc at the plateau phase, and then accelerating towards the Big Rip, and infinite rate expansion which will occur of the order of 10 billion years hence.
Now, such Robertson-Walker-like metrics are normally associated with a uniform density of matter. This matter density has to be an order greater than the visible matter density to explain the observed expansion rate; hence the Dark Matter hypothesis. But I don't need any Dark Matter. I get the expansion due to the mass of the Black Hole, 90% of which is already at the central singulaity, or at least nearer to it than we are - which means it is displaced in time from us to our future, and that is why we can't interact with it.
Now, the orbits of stars around galaxies follow geodesics of the spacetime, and they in turn are totally determined by the metric. So, they will conform to the geodesics of a universe filled with Dark Matter even though it's not, as the math can't tell the difference. Thus anomalous galactic rotation explained.