First, you need belief for any religion. GOD is not something that can be studied or evaluated by science, it's not an area where you'll find much objective evidence.
However, I'm presented with the idea of a loving, benevolent God... who condemns souls to damnation for simply not believing in the right idea.
We covered that very question
Here.
In a similar manner, I cannot comprehend the portrayal of mere thoughts and feelings as sins that separate us from God.
I would tend to agree in most cases. If it is an uncontroled thought I doubt that it would be considered much if any of a sin. The limitation for me would be an intentional
act. If you set out intentionally to have certain thoughts I could see how that could be a sin. One example might be planning and fantacising about doing major harm to another.
Aslan is not a Tame Lion