-Yuki-The-Emo-Kid-
1: Has anyone ever SEEN God? No.
2: Has anyone ever HEARD God? In the bible, but for all we know that book could be as inaccurate as a blind guy with a gun.
3: If there were a God, would he let us kill each other, seeing as we are all "God's children"?
4: Would he let global warming continue?
As you can plainly read, there is no God.
Half of what I've read from you here is just questions. Not exactly the way to come to a conclusion.
As for the other two: people have very different views of how to 'see' and 'hear' God. Technically you can't 'see' God because he's a spirit but I'll translate what you said as seeing a direct action from God. Some look for giant thunderclouds in the sky saying "I AM HERE" or something to that extent. Some recognise the real messages that God actually gives.
Sometimes you just gotta look for the little things, the little miracles, and there's your answer. God doesn't do a big show. That would make the whole faith thing far too easy. Also, he contacts us through feelings and spirit, not always through what you can physically see and hear. I guess the best way to get an answer from him is to wipe out any expectation one might have of what he should do, or is going to do.
And also: timing can be everything when it comes to God. Just because he doesn't do anything the first time doesn't mean any hope of his existance should be shut off entirely.