Abdullah,
I have no problems answering your open Challenges, 1, 2 and 3 and I will answer them, but I am wondering if you are the author of the answering christianity.com website, as I see the challenges are lifted directly from there.
They are valid, though misguided challenges, and I'd like to throw a challenge back at you.
Most of the content of these challenges do not reflect an understanding of the Bible at all. Therefore the challenges themselves do not lend credibility to your attempt to show the corruptions of the Bible.
Is it possible for you to stop looking at such forums, return to your own Qur'an command.. and take a Bible and with no reference to any Muslim critique of what you are reading, let the Word of God speak to you itself.
It will!!!
As you read things you are puzzling about, instead of trying to make the Bible prove Islam to you, which you are doing, let the Bible do what it is meant to do.. and reveal God to you. Ask questions and throw challenges, based on your own personal exploration, rather than ones meant to trick us.
Those challenges you have quoted are well documented, and I could easily just find a website and reply specifically on every point you have raised with equally credible responses. I would do that if you want me to.
However, much more important than all that, is that you yourself go and explore God for yourself and let Him speak to you. He said "if you seek me, you will find me, if you search for me with all your heart."