How could I get my son returned to me if my ex husband will not give him back?

I don't understand how neither of you could have custody, when you have 77% placement. Presumably that came from a court order which also determined legal custody. First, consult the lawyer who represented you in the divorce. He or she knows more facts than this site could develop. Your lawyer will probably suggest you bring an Order to Show Cause for Contempt against your husband. Document a demand for the return of the children by sending him a polite but firm demand letter, certified mail, return receipt requested, stating the dates and facts, and citing whatever part of your Marital Settlement Agreement or the divorce judgment which governs the situation. Insist they be returned within, say, 72 hours of the date and time of the letter If he does not comply, use the contempt power as soon as you can after the expiration of the time. Retaining a skilled matrimonial attorney would be a very good idea. Good Luck.

You need to talk with an attorney. Sometimes the police will help you if you try to pick the child up, sometimes they won't. Generally, it is considered a civil matter and you may need to file something with the Court.

You need to immediately file for custody. Hire an attorney to help you.

Your post is illogical. Call the police/sheriff to enforce your rights. If you don't have any custody order, obtain one.