Your next step is to hire a lawyer. You should have done that already. Unless you know the burden for justifying a removal, you are in trouble unless your ex simply fails to participate in the case. Removal cases are not easy. Why would you risk doing this yourself?
would you try surgery on your son step by step by asking questions of an on line service? this is somewhat analogous.
if no response is filed, do a motion for order of default. give notice. set a court date. if the resp. shows, she or he will be given time to respond. if a response is filed, then do a motion to set a trial date. the judge may appoint a lawyer for the child, or a guardian to investigate, or a 604 advisor to report.
read eckert and collingbourne ill. sup. ct. cases on what you must prove at the trial.
You really should hire an attorney. Removal cases are very tough to prove. If he does fail to appear, you can request a default judgment - just make sure he was properly served with the petition. Even if you obtain a default judgment, your ex can request that it be vacated within 30 days.
Nothing in this post creates an attorney-client relationship. This post is not meant to serve as legal advice.