How can I dispute a child support order?

Last week, I went to an Order to Show Cause hearing brought by the Department of Child Support Services two counties away, and argued that California's guideline could not produce a fair result in our case because I already voluntarily shoulder a large portion of the children's expenses with incomes roughly on a par and my timeshare only 30%. The DCSS manufactured a lower income for the other parent by underreporting earnings and claiming an inflated federal tax liability in their initial petition. I truly believe that the inputs to California's guideline calculation cannot provide a sufficiently nuanced picture of our situation to avoid doing harm to my children. But the Commissioner hearing the case shut me down on point 1 of 7 that I had ready to present. I failed at arguing against application of the guideline, and meanwhile I didn't get to challenge all the bogus inputs to the guideline. The county lawyer and DCSS social worker had a field day twiddling inputs to maximize the judgement (using court resources all morning while I waited). The other parent wasn't held to the same standard of disclosure as I, bringing only one unrepresentative paycheck. While I was informed (in the summons) that I had to file an income and expense report with 2 months of pay stubs and a tax return, signed under penalty of perjury. Do I appeal? If I apply for a change order can I subpoena the other parent's pay stubs, do I need an agent of the IRS to testify that tips are in fact taxable?