A Christian believes in the trinity. We are only Christians in the sense that we accept Isa as a prophet and the messiah. After that, the similarities between us and Christianity end. Christianity believes in a triune god (i.e. polytheism, regardless of how you cut it). Most of Christianity rejects the importance of deeds, whereas in Islam, both imaan (faith) and a'maal (actions) are necessary. Most of Christianity even rejects the laws of the Old Testament and since the New Testament we have today is lacking in any real laws, there is no law of God in the New Testament we have today.
Why are you listing the Hindu Upanishads as part of the revealed scriptures? The only books that we know for sure were revealed, excluding the Qur'an, are the Torah, the New Testament, the Psalms, and the scrolls of Abraham. Also, the ranking that you have listed is also something that is not agreed upon and is actually very controversial.
The source of Islamic law has always been Qur'an, then ahadeeth, then Ijma', then Qiyas. To change this order is to introduce a perversion in the law. Qiyas is almost always the last resort because it is highly dependent on the limited understanding of mankind. Also, you've placed the Qur'an below Ijma' and Qiyas - how on earth can you justify such injustice? The Qur'an is the literal word of Allah . To say that the opinion of majority or the analogies of a scholar supersede explicit instructions in the Qur'an is not part of Islam.
The Qur'an is always the first reference. If something cannot be completely derived from the Qur'an, the ahadeeth are brought into play. If there are still misunderstandings, then consensus of the ulama is followed. If there is no consensus on the particular issue being researched, then only does one rely on one's limited rationality to come up with an understanding.
And this is coming from a Hanafi, a member of one of the madhahib that has had a notoriety for relying upon Qiyas.
Also, the brother is right that if a person believes in tahreef of the Qur'an, such a person has left Islam. Even according to your mindboggling ranking, such a person would be considered a kaafir because there is Ijma' on the kufr of someone who believes in tahreef of the Qur'an. Allah himself says in the Qur'an that He will safeguard it so to believe that He did not safeguard it resulting in the changing of the Qur'an would be a slander upon Allah and outright kufr.
You also seem to have a grossly poor understanding of the ahadeeth. The Qur'an points to the ahadeeth, when it commands us to follow the Messenger , to obey him, to follow his example since he is the best of examples. To reject all the ahadeeth is also kufr by consensus. Without the ahadeeth, we don't have what the Qur'an points to. We don't have the Prophet living with us now. What was the point in sending a messenger if all his actions and words are irrelevant to our time? The Qur'an could have easily been sent directly as a compiled book, descending from the heavens, but it wasn't. The practical example of the Qur'an was Rasoolullah . What you're suggesting is that he was redundant!