I'm going to disagree with you that OP has to provide discovery on assets, bank accounts, or investment accounts unless ordered by the court. The child support orders are based only on income. That can include all sources of income but not the ability to pay from assets.
See 1240—2—4—.03 GUIDELINES FOR CALCULATING CHILD SUPPORT AWARDS.
A tax return is all that is required at this point. The attorney is just blowing smoke.
Collecting a judgment on support arrears is a different story but this is for a modification of support.

