Of course I had to see that after I'm done doing everything by hand...
Did you try any of the other implementations of the paper?
Did you ever try with a g2.8xlarge instance? 600px seems a little low res for printing.
How much GPU ram does the g2.8xlarge have? For printing an A4 at 300dpi you'd want 2480 x 3508px. If that doesn't fit in the GPU ram, and you are just doing this for yourself/friends it might be a better idea to run neural-style in CPU mode.
An order of magnitude slower but you'll have a lot more ram at your disposal