You quote to me a scripture, 2 Cor. 13v1 using this in the dishonest JW way (as with 2Tim 3v16)
Paul in 2Cor 13 is talking about 2 or 3 witnesses proving to him the problems when he gets there. Not talking about procedure that should be followed by later congregations, he is simply saying he will not act against sin that is not corroborated properly.
Ref 2Tim3v16 What was Paul referring to ? not his own letters surely.
And yes, he was saying the principles found in all the Jewish scripture, which would include more writings than you have in your NWT, were useful, valuable , but he was not saying they had to be slavishly adhered to when they evidently do not work, as in child rape cases.
Paul argues at length that the Law is finished, fulfilled, in the Christ so taking a bit of it and making it a rule, goes against a belief in Christ.
He is encouraging a study and use of scripture,by Timothy, similar to the Jewish method of Midrash, which, if properly practised, would not make the mistake the WT does of following to the letter little bits that suit them.
Please look at the context, don't just pull verses out and quote them to fit your argument, I had 58 years of the WT doing that, and it stinks.