The Bible doesn't get everything right. But you're correct, the most important thing to draw from it is to have a personal relationship with God. The purpose of the Creation story isn't to tell us historically what happened, but that God created us. Whether it be through the big bang, evolution, etc.
I have to point out that your statement about IQ being fixed at birth is incorrect. That is a very old biological argument, and we have many studies demonstrating the plasticity of the brain and that IQ can be improved or lowered given certain factors. I would be happy to send you some studies on this matter if you like. Yes, an atheist is closed minded, but they are not the most unscientific - you are basing this off of the single concept of the big bang theory. Christians can be just as closed minded and more scientific, denying modern medicine, evolution, and adopting the early Biblical stories as scientific fact.
The reason Jesus came wasn't to better understand us - he created us! From Jesus we got to know a side of God that we couldn't have otherwise - we got to develop a personal relationship with him. We got to know the depth of his love for us, that he would ultimately die for us, no matter who you are, no matter what you've done. So we get to understand God as a merciful, kind, and loving God that we just didn't see in the Old Testament.