What is bothering me most now is that if Earth is 100 pixels wide then 1 pixel is 127.42km and Mars should be something like 54600000/127.42 = ~428500 pixels aw

What is bothering me most now is that if Earth is 100 pixels wide then 1 pixel is 127.42km and Mars should be something like 54600000/127.42 = ~428500 pixels away, not the claimed 857000. The radius of planets has been used where it should be diameter and this error seems to have been carried forward throughout the demonstration. EDIT: This has now been corrected - nice one!