I was raised in a Southern Baptist church, completely lost faith and was agnostic, then had a religious experience a few years ago and returned to faith.
I don't believe everything the bible says for the reasons you have pointed out. I don't think that only christians go to heaven. I'm not even sure what "heaven" is.
That is part of faith to not have to have all the answers laid out in front of you and to still love God. Why love God? Why believe? Because deep down in our hearts all men know that love, faith, kindness, and altruism are right and good and born of the Divine.
This isn't to say that Christians, Muslims, Buddhists, etc instantaneously become perfect God like beings. We are still flawed. Some murder, many lie, many cheat, etc. This isn't the word of God causing us to be this way. It is us exercising our free will in a destructive manner.