So there was a lot there and I didn't read it all but if that one question still stands...
I believe Jesus Christ was God incarnate, second in the Holy Trinity. I believe he was crucified by the Romans upon the pressings of Jewish leaders who disliked his radical teachings. I believe that during this crucifixion Christ underwent insufferable pain and agony, pain equivalent to the combined punishments of all the sins, all the billions of sins that had been and would be committed all to the end of time. He suffered the punishment for all of those. God's just punishment was moved from us, consolidated into one huge punishment and poured out on to a blameless member of the Trinity, who willingly underwent said punishment.
The Triune God, then, resurrected Christ from his grave, whereupon Christ explained what had happened to his disciples and implored them to spread the word the the world, that they might accept the atonement pre-emptively made by Christ Jesus. And so the apostles did, working vigorously and without fear of their own horrifying deaths to spread the gospel far and wide, lest Jesus' sacrifice be in vain.
I believe that every human is infected with evil and will committ inumerable sins even in the shortest of lives. I also believe that the just punishment for even one of these sins is eternity in anguish. Before I continue let me clarify. A sin is an action you KNEW was wrong when you did it, but did it anyway. We have all felt it, doing something wrong, the rush almost that we get, the guilty pleasure when we get away with it and the sinking feeling when we don't. That is sin.
Anyway. Each of us does hundreds or thousands of these and none of us deserves any good turns whatsoever. But God loves us nonetheless and made an unbearable sacrifice for us, which he then planned for humanity to hear and receive. I have heard, and received this message, and I am grateful that I have, indeed, been saved. You may hear Christians throw that word around, saved, but the reason that was the word of choice is because we were indeed saved from an awful fate by a benevolent God.
Now. I believe all of this for a few reasons. One is, the message itself is irresistable; indeed it was designed as such. Two, the Bible has a lot of evidence to back it up. As a historical text it has proved itself over and over, and its accuracy from the ancient text to today is undisputed.
There are thousands of manuscripts, unconflicting, of the ancient books, whereas there exist only a few dozen of the Illiad and Odyssey, and they DO conflict. So I believe the Bible. I will probably we lampooned and roasted because I have holes in this, but that is because I am running late and didn't put a lot of thought into this.
One thing I'll say for sure though, most non-Christians seem not to understand fully the meaning of "died for my sins." It's one thing to intellectually understand, but to fully understand, unbelievers just don't seem to make it there, which, in my opinion, is why they remain unbelievers.
"Oh, the joy of sins forgiven."