Very deep questions... all which would take VOLUMES of these answer sessions. I will try and simplify though.
Believers know that God exists simply because we can see Him in everything good in the world. Its no accident why why trees are so green and the sky is so blue. God does not make the evil things of the world happen...death, war, bloodshed, disease, atrocities of all kinds. People make these things happen, usually over power and greed... and sometimes its time to go home. God said that he would not stop it from happening if we chose it. That is why we are here, to experience freedom of choice. Unfortunately, lots of us didn't chose war or greedy warmongering. We chose peace but are unable to live it in all aspects of our lives.
God is not a torture device. He NEVER gets pissed. He is all loving and wants better for us but He knows that we need to learn the lessons before we return home to him. People tend to forget that he desires a conversation with us just as we do with others. He is there waiting patiently for us to come to him for peace in our hearts and souls but lots of time we get caught up in our own lives and forget Him.
Yes...some people only believe because they were told that is the way it is and they have never tested the theory of His existence. If you live in blind faith, you will eventually fall to ignorance and others attempts to blindfold you from the truths. Your testimony has to be tested. I mean to literally question his existence and let him prove it to you. I am not speaking blasphemy here. He will do exactly that. I'm not talking telling him to start the rain or move a mountain for you... I'm talking about asking Him to prove to your heart that he is real and he will fill you with a feeling that you have never experienced before. And once you have had that feeling, you will never forget that He exists. I don't believe what anyone says over the pulpit or in Sunday School without confirmation, after all, its the teachings of man, mingled with scripture. I ask for God to convey its truthfulness to my heart.
BTW... my faith says that Hell is only a place for those who KNOW GOD AND DENY HIM. That means that you pray for knowledge of His existence and he gives you undeniable proof and then you make it your point to try and destroy His word and His followers. Yes, thats evil sounding but thats what I believe. Why would God, who unconditionally loves His children, suffer them to damnation for something silly and HUMAN in nature. Thats not the point of our existence here.