Hey Marlene,
DH has a business too, we dont dodgy the books, but his income at the end of the fin year is always a lot less than is reality... due to the profit and loss situation of the business (its not a company)
Unlike most men, DH is happy to contribute to the cost of raising his DS... One year he had to again go to the CSA for an interview as the assessment came back as saying he need to pay something like $20 an month, there was no way that we believed this fair and continued to pay the amount that was set for the previous year... the reason that it was reassessed was that his earning CAPACITY was greater than what was reflected... can you not ask for a reassessment on those terms.

I know that most women and mothers have it really really tough, and we (DH and I) have a huge dislike of those men that cant take responsibility for their kids - it means that he is unfortunately lumped in with a$$holes that are out there.

Sorry for your situation