I would not interpret the Bible using your opinions. The very same goes for Joseph Smith. I believe that no one is saved trying to obey the Talmud.
Which stands in stark contrast to what the first believers in the Tanakh/Old Testament held to be true. Your interpretation is different from the original.
Following the LAW is rewarding in this life. One may live longer. The fact remains that CHRIST is the final sacrafice. CHRIST fulfilled the requirements of the LAW for those who will accept HIS remediation. Those that do not are under the full weight to fulfill the entire requirements of the LAW themselves. The book of Mormon seems to have no scriptural support to stand upon. It seems to have no historical evidence to stand upon.
Much of the Bible is lacking evidential support as well. IMO, it's mainly the passage of time that's made its factual claims seem a bit more reasonable.
I would not interpret the Bible using the Koran. Why exactly is that? Could it be that the Koran does not fit the tone, direction, message, etc., of the Old & New Testaments?
I don't see why that would stop you, since you already interpret the Tanakh using the New Testament despite their very different tones, directions and messages.
There is much more historic validity for the Koran than can be found for the book of Mormon...
Sure... there's plenty of evidence that Muhammad was a real person. The problem that the Quran, the Tanakh, the Gospels, the Epistles and the Book of Mormon all get into, though, is that there's no evidence that they came from God.
You criticize the Book of Mormons for what you see as its faults... fair enough by itself. But what you apparently fail to realize is that the scriptures you hold up as holy also have similar faults. You condemn the Mormons for things that you and most other mainstream Christians also do.