Father grossly misstated income

I am looking at being ordered to pay 800 a month in child support and only make $25K per year. My income last year was $70K but I had to move to be closer to my children and now am grossing about 25K per year. In court last year he was asked what his income was and he stated 24K. The 24K was AFTER expenses. When I got a copy of his tax return the income was 154K - he files a 1040 and is the only member of an LLC which is his business. he ownes a motel and lives there, so he pays no rent - the business pays the mortgage. I have heard that child support is based on income prior to deductions. Would this guideline still apply to him? He files one tax return for his business and personal together. I am willing to support my children, but his business makes a lot of cash that he doesn’t claim and I am barely paying my mortgage and health insurance and basic living expenses. Our current order states that we have joint custody and because I was living 140 miles away he has the children during the week and I have them on weekends. I am filing for a modification of custody since I am now living in the same town. Can you please shed some light on this my attorney can offer no help.

Child support is based on gross income, before any deductions. His receiving free rent, will also be factored in as “income” as it is a monetary benefit he receives regularly.