I could be wrong but I think the arrow keys move 0.25 in space (someone correct me if that isn't true) so move it 4 times if you want to move it by 1
I think it varies depending on the mesh, so I don't know off the top of my head sorry
the only way I think is looking into the text file that is the model, but then you cant easily distinguish the vertices apart
the model coordinates only relate in whatever way you use them, if you have a 1x1 plane and apply a 64x64 pixel texture to it, and then a 128x128 pixel texture, the first will just look more zoomed in if that makes sense? the bigger the texture, the more it gets 'squashed' to fit the face of a model you're applying it to (I recommend just messing with them to see how it works :) )
