First of all, one version cannot be compared to another to get any realistic understanding of whether something is wrong or missing. KJV and NIV side by side doesnt tell us anything. BOTH could be wrong.
Any translation has to be compared to the Greek / Hebrew manuscripts to know if something is missing or rendered incorrectly.
Wrong. You might as well throw the bible away if you don't know whether or not it's the word of God. God showed us at Pentecost that he is perfectly capable of passing along His word in any language. God is absolutely as present in translations as he was in the original manuscripts. He didn't just reveal himself to those who spoke Hebrew and Greek. he has revealed himself to all nations. All one has to have is the indwelling Holy Spirit to discern the truth of any translation.