As for the Walmart thing, not all Walmart cashiers make between $7 and $9 an hour. They certainly don't in VA and NC. It's closer to $6/hr.
However you mentioned that she was a security guard but even they make less than $10 an hour.
They are going to take into consideration the fact she can't return to law enforcement. And they are going to look at the job market in the area and what she would be able to do. And let me tell you, the job market in NC SUCKS! So I can see why they are imputing her at minimum wage. Although personally, I think they could go a dollar higher, not like it would make much difference. What was she making as a cop? Like $25k a year?
If you were making income in the gray shaded area of the child support guidelines, they will not even take the CP's income into consideration at all. That gray shaded area also happens to mean that the NCP is not making a lot of money. That's one thing I hate about NC. I don't know what idiot made those screwed up guidelines. If you were making $800 a month and she was making a million a year, they would not even figure her income into the calculation. Can you believe that crap? Anyway, it sounds like you don't fall into that category.
Just don't expect them to impute her income too high. If she does get an increase, and that's a big IF, then it probably won't be much. JMO.