But the question is not THAT easy, is it? If you say that something is a false translation or mistranslated - then compared to what? Or to which translation? Can we say that a translation is wrong, just because it differs from an older translation? Just because a translation - as a whole or of a certain passage - is old and/or widely used, it does not have to mean it is correct. For each and every NWT verse some would choose to call a false translation, one could just as easily point to other verses in other versions or translations and call THEM false translations. There is a huge difference between a translation which is different from how the verse is translated by other versions of the Bible, but where the transalation is within the realms of what is possible - and a translation where grammar rules and word meanings seem to have been deliberately broken or changed to force the verse to state what your pet opinion wishes it to state. John 1:1 is no example of the latter, and neither are 90 % of the so-called examples of falsely translated verses in the NWT. I think you should start by reading Jason BeDuhn's Truth in Translation.
We do not speak KJV English any more. Languages change. New manuscripts are found. Our knowledge about the world 2,000 years ago increase. If you do not speak NT Greek yourself, you really are in no position to utter an opinion on the matter, because you then have to rely on what experts say, and you have to "pick your experts", choose between them. As long as you do not master NT Greek yourself, all you have is hearsay.