I understand what you mean about how it seems odd that in this case scripture was added, but if the story is true (as I believe it), then the full truth was not the earth, and therefore had to be brought to light, or, so to speak, fill in the holes. Absolutely one must test spirits and prophets, but we also cannot prove everything there is to know about the Bible, either. Testing spirits has a lot to do with feeling. Somewhere in the Bible (can't remember where right now) it says that if something is true, you will feel a "burning in your bosom." That's what people must test with the BoM, too. I've known people of other religions that were devout to that religion and became Mormon. I also know 3 people who were stongly anti-Momons and anti-Mormon activists that became converted. They all say they felt that burning in the bosom that only comes from asking God if something is true or not.
I don't remember saying that reasoning was excluded from faith or anything about blind faith. But in a literal sence, everyone who believes in God is following blind faith (in a sense). I mean, have you ever seen God? Has anyone you know ever seen God? I know I haven't seen him. All we're going on is what the Bible says and we believe to be true. Faith (in a religious sense) is blind because you're putting all of your trust in something you have not physically seen to exist. Though, don't get me wrong, I'm not saying that blind faith is everything. Personally, I don't look as faith as blind.
As for why we need a second authority like the BoM, it may be debatable that we don't, but it's support. The way I have heard it before, the bible and BoM are like nails. When you use one nail to hold a board to the wall, you can, but the board will spin. Having two puts another nail into the board holds is firmly in place (ie, like you life).
Yes, Revelation does say not to add or take away from scripture. But there are two things you must remember: first, the Bible is not arranged in chronological order. When the Romans arranged it, they did it in order of what they thought was important. Hence, after the five gospels they had (Matthew, Mark, Luke, John, Acts of the Apostles) they put the book of the Romans. With that being historically true, isn't it true that any book of the bible written after it would therefore be wrong? Also, what has also been said (by someone who was NOT Mormon, and I can't remember his name, but he was a Bible scholar) was that John could be talking about that if HIS teachings were changed. He was shown many things by the Lord (especially in Revelation) and if those things are changed or left out, then hellfire would rain upon us.
H-D