First problem: in corel, if you convert an object to a curve, you can read the length of the line in properties. Figure out how you will step through any given material, feed rate, passes, then divide the length of curve by feedrateXpasses. That should give you minutes. Then add tons of time for generating art files, loading the machine, changing a broken bit, and eventually you'll have a number that probably doesn't pay enough, but is cheap enough to keep the customer happy.
Second problem: sounds like what most refer to as steps per inch. Usually it's something more like 5,000 steps/ 1 inch. Send pictures of where you are looking at these values. Also calculate the highest distance your router will go, and check it with smaller values. Doing 20" will likely still generate an error of .005", which you can't much perceive, but at 12', that becomes nearly a sixteenth of an inch.