... Can you provide evidence that we are not living in a flat 2D universe and what we see and experience is a 3D 'holographic' representation? I bet you can not....

Contemplate a two dimensional universe. The only thing you could see would be straight lines (a dot being considered a short straight line). No shapes whatsoever, just lines, which i suppose may be blurry at a distance, such that you could distinguish which end of a line at an angle is receding or approaching. That you can see a square or a triangle from above - up but not north, is proof that we live in a universe of at least 3 spatial dimensions. Now try to imagine a universe with 4 spatial dimensions. With 1 spatial dimensions. With zero spatial dimensions. Interesting stuff, I recommend reading Flatland, available free online here http://www.geom.uiuc.edu/~banchoff/Flatland/