That is so easy! Its not like you cant find him to serve the papers. They will mail his copy out to the jail and they know that it has been accepted. Go ahead and file list his current address - jail and let the process begin. He can still try to make changes to the decree from there as he would if he was out. If there are children involved he will just look really bad to the judge if he tries to get anything more than you are willing to give and probably will not get what he is asking for.