Ah, where to start...
You correctly paraphrased Revelation. The key is that Revelation talks about adding to "THIS book." To what book would John be referring? You seem to think it's the Bible, but of course that can't be so, because the Bible didn't even exist at the time, nor was it really even in the works. Second, even if he was talking about the Bible (which he obviously was not), it has undergone countless changes throughout the years, adding and subtracting to and from what is considered canon. The Bible you use today has undergone numerous additions and subtractions, so I guess by using it you're in the same camp as those who use the Book of Mormon.
Of course, however, you're not, because logically the book to which John is referring can only be the Book of Revelation itself. It's a warning about changing or editing the revelation that he received. Of course, Mormons have not done this, because they believe the Bible is the word of God and believe in Revelation, having not changed it.
Your next point quotes Galations, regarding the preching of other gospels. Mormons do not preach other gospels, they (claim to) preach the true gospel of Christ. Unfortunately, many aspects of the gospel had been or were unclear - this really can't be refuted, how else can one explain all the various sects? Mormonism teaches what they believe to be the true gospel of Christ, unchanged (as Paul requires). Of course, this is what all the other Christian faiths do as well - they teach what they believe to be the true gospel, but due to the uncertainties in the Bible, the best they can do is teach their personal interpretation. Mormonism, on the other hand, at least claims to have input from God in clearing up these uncertainties. All other faiths, by their own admission, can only hope to be preaching the true gospel that Paul speaks of. Nothing was added.
As for visiting the Americas, in John 10:16 Jesus says that he has other sheep who will hear his voice. This can easily be seen as Him saying that he is going to the Americas. Oh, and your "recollection" of the Book of Mormon is (shockingly) incorrect - Christ does appear to the people in the Americas in the flesh. This is because he has been ressurected.
Next, you say the Bible doesn't address Baptisms for the Dead? Check out 1 Corinthians 15:29 (Or else what will they do who are baptized for the dead? If the dead aren't raised at all, why then are they baptized for the dead?). Sounds like the saints were performing baptisms for the dead, and from the context of 1 Corinthins 15, it sounds like the the leaders of the church approved of this practice.
Finally, you are correct that we should test the spirit to see if something is from God. However, it seems as though you have failed to actually apply this admonition. Your convictions seem to be based upon your interpretations of text and on what you have been fed by anti-mormon sources. Have you ever actually read the Book of Mormon to test it by the spirit, by actually praying and asking the spirit to let you know whether or not it is true? It seems to me that you are using the tests of man and not the spirit to reach your conclusions.
There are differences between Christian and Mormon belief.
Christians do not believe that Satan and Jesus were brothers.
Christians do not believe that men can become Gods.
It's dishonest to pretend that there's no difference.
That's all that's really being said here.
And insensitive as it may seem, ... it would be most unloving if noone on this thread pointed that out (particularly as it relates to one's rightness with God).
If God had said that it didn't matter what we believed ... it would be a different matter.
I grieve for the young men who were the victims of this senseless crime.
But there will be more reason for grief if God's truth is not heard.
Second, even if he was talking about the Bible (which he obviously was not), it has undergone countless changes throughout the years, adding and subtracting to and from what is considered canon. The Bible you use today has undergone numerous additions and subtractions, so I guess by using it you're in the same camp as those who use the Book of Mormon.
Not quite.
The Bible has not gone through countless revisions.
Second ... the books of the Bible were agreed upon by the unified church.
This has not been the case for the Book of Mormon.
Your next point quotes Galations, regarding the preching of other gospels. Mormons do not preach other gospels, they (claim to) preach the true gospel of Christ. Unfortunately, many aspects of the gospel had been or were unclear - this really can't be refuted, how else can one explain all the various sects ?
The Bible itself refutes the claim that it promotes uncertainty.
The Bible states that it is perfectly adequate for every christian belief and endeavor.2 Timothy 3:16 All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness:Mormonism, on the other hand, at least claims to have input from God in clearing up these uncertainties.
17 That the man of God may be perfect, throughly furnished unto all good works.
Of course the scriptures of the Bible claim inspiration by God (see 2 Timothy 3:16 above).
Also note the following scripture ...2 Peter 1:21 For the prophecy came not in old time by the will of man: but holy men of God spake as they were moved by the Holy Ghost.The claim of the champions of the Bible scriptures have been accepted by the church.
Joseph Smith's claim has yet to be accepted.