I have a simple explanation that, on the surface, explains everytthing without dark matter, leaking gravity, etc.
Consider that the light from the nearest objects being used for red-shift data left their sources long before the first red-shift measurments were made. Now, suppose that the expansion of the universe has already stopped, and the collapse has begun. Therefore, we are accelerating and receding from objects that appear to be spreading outward because, at the time the light left them, they still were receding from one another. The farther away the objects are, the faster they would seem to be moving away from us, since it would take longer for evidence of their slowing down to reach us. The nearer objects seem to be moving away more slowly because we see evidence of their deceleration sooner.
It's simple, it follows the laws, and it doesn't depend on any hidden matter or leaking gravity.
I am not an astronomer, but I did stay at a Holiday Inn Suites last night, so fire at wiil!!
If that was the case , you would think that the close galaxies like Sagittarius ( at just 75,000 light years )would show some evidence of that. Presumably, if the expansion ended, the collapse would effect all bodies within the universe in a similar fashon, us and our nearby galatic neighbors included. We should need to see things beyond the redshift to know what direction things are heading in.