FAFSA - - Ex-Spouse Pushing to Have My Infomation On Form Instead of His - Fishy?

If the parents can agree that the kid will start spending more time with mom so that mom can qualify as the custodial parent for FAFSA purposes, and if dad agrees to make a financial contribution to mom to offset her increased expenses if the kid starts spending more time with her, there is no reason to formally modify the custody agreement. Just agree what needs to be done and do it. Likewise, there is no reason for either parent to share financial information with the other parent. The FAFSA custodial parent completes the FAFSA using only his or her information.