2 Nephi 11 Questions

For me, the scriptures always make me ask more questions than they give me answers for. I told Stephen once that I may just be a better Christian when I'm not studying the scriptures & I just work to be nice. Anyhow, a question that came up for me today while reading was this:
If
3 And my brother, Jacob, also has seen him as I have seen him; wherefore, I will send their words forth unto my children to prove unto them that my words are true. Wherefore, by the words of three, God hath said, I will establish my word. Nevertheless, God sendeth more witnesses, and he proveth all his words.
(Book of Mormon | 2 Nephi 11:3)

is true, does the fact that there are many witnesses against religion negate the three or more witnesses in favor?

I'm not trying to play devil's advocate here, really. I'm just curious as to how you know truth if there are evidently witnesses on both sides. My gut tells me it all boils down to the spirit...but then, why do different people get different answers?

7 For if there be no Christ there be no God; and if there be no God we are not, for there could have been no creation.
(Book of Mormon | 2 Nephi 11:7)

I read this line in faith...(and it makes me wonder why evangelicals are against the LDS religion...perhaps they haven't read the Book of Mormon?), but I fail to see how you could prove the importance of faith in Christ via this statement...it seems to me the faith must be in the whole picture at once, one part cannot really prove another. The whole story either has to be real, or not. Telling someone they exist because of Christ, when they already believe they were part of primordial soup does very little to convince them of the atonement. Just my two cents.