I believe the Bible teaches that it is the
inspired word of God not a direct dictation (as with the Koran), and I agree with you that modern translations may contain flaws...only the original texts were "inspired".
http://carm.org/manuscript-evidence
Having said that, I think we have an abundance of tools at our disposal these days to pick apart the texts and decifer the teachings of the original texts to a very high degree of accuracy.
In the same way, Islam claims the Koran is without fault in its original translation, but looking back into the history of the test itself, there is a lot of dispute over its accuracy & completeness.
I find it very interesting that you would choose 1 John 4:1-3 as references. If you continue to read the chapter, you'll reach verses 9 & 10:
9 In this the love of God was manifested toward us, that God has sent His only begotten Son into the world, that we might live through Him.
10 In this is love, not that we loved God, but that He loved us and sent His Son to be the propitiation for our sins.
This seems to be a pretty strong arguement against Islam. John is saying, "watch out and don't be decieved, if anyone denies Jesus is the Son of God, he is that anti-Christ". Having read this, do you question Muhammad's teachings? Why or why not?
Concerning Deuteronomy 18:17-19:
This could easily be attributed to having been fulfilled in any or all of the Old Testament prophets.
Reading a bit further also provides some interesting insight v19-22: it could be reasonably argued that Muhammad does not pass the test. For instance, why didn't the Dajjal appear in the 14th century as Muhammad prophecied? Or why are Muhammad's moral teachings different from Jesus'?
Concerning Isaiah 29:12:
If you add in verse 11 and read the whole passage in context; it is not a direct prophecy, just simple truth.
Please keep Biblical references in context, and I will give the Koran the same respect.
Concerning John 16:7:
Again, read the whole passage...Jesus talks about returning to His father, but you conveniently skip over those parts. Verse 7 is referring to the "Holy Spirit", part of the trinity which Islam rejects. But if Jesus is teaching it, how can you reject it? How can you say that Muhammad was a "comforter" or "advocate" when his teachings are so different from Jesus'?
Concerning the gospel according to Barnabas:
If you're really quoting this as a legitimate source, are you aware of it's inconsistancy with the Koran?
http://www.albawaba.com/editorchoice/gospel-predicting-islams-coming-contradicts-quran-414781