Your question above does not sound like fraud if you agreed to a deal less than one to which you were entitled. However, whether his increase in income would be considered substantial is within the judge's discretion. If the State had an interest in this matter, I am surprised that they allows you to a hold open of child support with such a disparity in incomes.
With such an extreme income disparity, child support is normally paid. Particularly when one party receives state aid. I agree that the child support agency is usually involved in these instances, but if not, there is no reason you cannot try to modify support yourself. There is no magic number for a change in circumstances to modify support, but I see no reason not to request a modification. A difference of $7,000 in a year could certainly meet the "substantial change" standard.
This submission is not, nor is it intended as, legal advice. You should consult a lawyer to address your legal issue.
You shoud probably contact CSA and ask hypothetically, or seek a local attorneu and get a free consultation. My experience is it usually takes 15% or greater. But with number this high it might trip sooner than that. Try CSA first. They sould be willing to talk off the record.