Revised child support/custody

Yes, it can be done.

As to child support, Illinois law allows child support orders to be modified at any time until the child reaches eighteen.  In order to modify an award, the moving party must persuade the court that circumstances have changed substantially since the last support order was entered.  "Circumstances" usually means that the father's income level, the child's needs, or both

As for child custody, along with best interests of the child, stability and continuity in the child's custodial and environmental relationships are key concepts in Illinois custody law.  There is, however, a strong legal presumption in favor of the existing custody arrangement.  To overcome the presumption, one of two facts must be established: the custodial parent must be adjudicated unfit to retain custody, or a change of circumstances since entry of the previous custody order must be shown which directly affects the child.  A mere finding that modification would be in the child's best interest is insufficient.  Facts and circumstances which existed and were known to the parties prior to or at the time of entry of judgment, or a change of circumstances in the life of the non-custodial parent alone, are insufficient to support a change in custody.

Custody may be modified only upon a showing by clear and convincing evidence, based upon facts that have arisen since the prior judgment or that were unknown to the court at the time of entry of the prior judgment, (a) that a change has occurred in the circumstances of the child or his custodian, or in the case of a joint custody arrangement that a change has occurred in the circumstances of the child or either or both parties having custody, and (b) that the modification is necessary to serve the best interest of the child.  These criteria apply in any proceeding for change of custody, including a petition to change from joint to sole custody and where both parents have moved for modification.