The proof I have is the Bible. It was not written by "some dude" it was God breathed which inspired men to write it down in words.(2Tim. 3:16) How can you be "spiritual" and need proof for everything? You need faith-trusting in something, though you might not see it. For example- is there a Japan? Yes. How do you know? Have you ever been there? (If so, replace Japan with somewhere you have not been) No you haven't. But, you believe it's there. Interesting...
Adam sinned. You agree. Therefore cursing the entire human race. Now, don't be asking "well, why!? etc..." Just accept it, cuz you know it's true. So because Adam sinned, we also are sinful from birth. Our own nature is evil, and the intention of our heart is wicked (Jer. 17:9). Everyone deserves a just punishment for their own sin. That punishment is Hell, eternal misery, eternal separation from God, etc... But, God being rich in mercy sent His only Son to live a perfect life as a man on this sinful earth.
Then you said "Why didn't God be more merciful and save everyone?" (Look up mercy in the dictionary.)He could, but He didn't. One reson being- when people are in Hell that glorifies Him. "How?" Because that is His wrath being satisfied and poured out on unworthy sinners. God is a just God and gives each action its right punishment. That is why Jesus had to be human, fully human, yet fully God. He had to be so that sinners might be perfectly redeemed.
God... blood thirsty? I don't think so! As said before, we all deserve Hell. God is sovereign He can do whatever He pleases. (Ps. 115:3) They deserve Hell anyways, right?
Well, just letting you know and I hope you believe it, because if you don't- you are denying your creator. The Mighty God. The eternal Father. And if you haven't truly repented of your sins, turned to follow Christ with your whole heart, then His wrath sure will be satisfied with you...