In order to get a name change for the child he must petition the family court in your state and have you served with a copy of the petition. He cannot just get the name changed by himself. And even if he petitions the court for the name change there is no guarantee the court would grant the petition over your objection. Indeed, it’s more likely that the court would reject his request.

Until he gets a court order of custody or visitation you don’t have to let him see the kid at all. If he goes to court seeking visitation you may contest the request and try to get it denied or at least get court ordered supervised visitation.