My two cents. That may or may not work. I think that you are preparing a lot, but may not be preparing the right information or approach.
What are you debating for? Do you want to convince him that he's wrong? Do you want to state your educated reasons why you don not believe? Do you want the debate to be an ongoing thing? What do you expect to happen at the end?
Then, before stating and giving anything you have, I'd start by listening to him first. I start with asking questions. Sometimes what you get is some kind of testimonial, some story about how wonderful their lives are after finding their god, etc. That information is important to you because that's what you should be addressing or at least acknowledging. If people hold on to nonsensical believes because they feel safe, or because their religion is what gave them peace of mind, or a safety net away from a lifestyle that they feel otherwise they couldn't change, there's no logic and information or teaching, or history, or documentation that would make them change their mind. To them it's not about education or information; it's about what the religion gives them.
Prepare to listen to what he has to say to understand what they actually believe and how he applies those believe to his life, along with why he's so convinced about his believes.
