In my opinion I don't think you can prove i"the Christian God" exists. With Christians it's a matter of faith. Proof or not matters not to them. They have a belief that focuses on the unsean. Even if you were to see an angel and get it on tape the other side might say it's just a fake with current technology you can manufacture anything. But the other side believes what they believe.
People can be closed minded regardles if they say they are not. Because they might simply be asking you to prove them wrong simply to give a reason to validate their decision they already made. Kinda like how some wil go to the doctor and he might say you have this and this is the only treatement. Well the patient might think another treatement is all that is needed. They'll then go from doctor to doctor until they find the doctor that agrees with their opinion they already made.
And finally one man's miracle is another man's ah that person just had really good luck. So I don't think either way you can decide the debate. One side is focusing more on faith than proof. The other only cares about proof, and won't want to just have faith. And again others are simply looking to validate their opinion. I don't think it can be decided either way.