I think this one will be up to the court. Some courts require exchange of tax returns and others don't. You provide him with your tax returns as well, right?
The way the guidelines are written, a parent just needs to provide some financial information upon request. I don't believe that gives every parent an open ticket to request anything they want. However, if your attorney were to motion the court for the information, I would imagine he would need to provide it. Typically parents would be required to exchange information, so it's a two way street.
Also keep in mind that only employment that was established during the marriage can be used for child support. Other side businesses may not need to be included if he has recently started these businesses as a means to recover his child support payment and make ends meet.