I cannot answer your question specifically to the laws of Indiana as I am not licensed in that State. In my jurisdiction a child can testify concerning his/her wishes when they can understand the oath to tell the truth. Outside of abuse issues, it is frowned upon to bring a very young child into the court. Generally around the age of 12 years old, a court will listen to the child's wishes. However, the child's voice is often like a whisper. As the child matures his voice becomes louder. Many cases have started and failed based upon a child telling one parent that they want to live with them and then when it is time to go to court the child changes his mind or there was a misunderstanding. I have witnessed a child state that he wanted to live with dad, but really just wanted additional visitation time. I am slightly confused by the facts presented. If father already has four overnights each week, he has the majority of the custody time and outside a huge difference in income would receive, not pay child support. To begin the process you would file a Motion to Modify Child Support and Child Custody.