The thing is, the message we get from the bible IS based on our interpretation, to a greater or lesser extent, whether we like it or not. Different people will place a different emphasis on what they read and how they use it to influence their life.
The message that is most important for me is love God and love my neighbour. Now I'm absolutely crap at it, but I'm doing my best when I can remember to do it. Actually no, it probably isn't my best, because otherwise I'd probably sell everything and go and do something like Mother Teresa. My family wouldn't be very pleased though!
Someone else would place emphasis on being baptised, and say that is the only way to salvation. I for one, despite what it says in the bible, would not like to make a judgement on someone being condemned for not being baptised. That judgement is for God to make.
The point I am trying to make is, and I'm agreeing with you on this, that none of us REALLY TRULY know anything for sure, except what our faith, our belief in God is telling us and also how we interpret, or have interpreted for us in some cases, what's in the bible.
You might consider that a very poor reason to be a Christian, but so many of us have felt our hearts touched by God, and the presence of God in our lives; it IS generally more of a heart decision rather than a head decision, although you'll probably find some Christians who'll disagree with me on that too!