What happens when solar systems start crashing into the "wall"? Well, first off it is whole galaxies, not just single solar systems.
Second, what happens is that they bounce off just like the radio waves, and come careening back at random angles toward the center of the Universe.
That explains why not all galaxies are moving AWAY from the center of the Universe.
Since you seem to be well versed upon the inner-workings of the universe, when we view the images of the galaxies and their direction of rotation (some being clockwise and others being counter-clockwise) - is that due to the fact that some are being viewed from the top and others from the reverse side? (and in reality they all spin in the same direction)
Inquiring minds would like to know.