.....the Bible is the infallible Word of God....the contents of our Bible took several hundred years for it to take the shape that we recognize.....
I am not as certain as you are about how the Mormons place the Book of Mormon in with relationship to the Bible
The Bible says that God was and has always been in more than one place, the Bible says that Jesus is the son of God and died for our sins, The Bible says do not believe the word of man ( false prophets ), the Bible was written by men who were inspired by God or were eye witnesses to Christ’s life. Christ said that the Word of God is infallible and the Bible is the Word of God.
Either you believe or you do not it is your choice. Mormons can call themselves whatever they want, they are not Christians by a biblical definition.