To find out what images are in the final build export it and look in the images folder.
There are different levels of minifying, I can't say for sure which C2 uses but if a variable is never referenced it should be automatically removed. You could try find an example, open the js file for editing and search for it to see.
[Note some minification will rename variables to shorter names too and not as you wrote them]
Calculating the distance will be negligible, however displaying it every tick would have some impact, instead update it every second or so.