2=> It is difficult to explain how to do it, it will require some coding modification. In this case, I think you should ask a developer to help you . If he know Joomla programming, he should be able to modify code easily to add the image .
In most cases the "Coupon Code" is at the bottom of a form. This is just a suggestion - why not put it at the bottom as a default instead of having us move it around?