Just a question and a suggestion for a start:
Do you think the New Testament texts were accurately transmitted? (yes or no, why and how). Yes, so many copies were carefully made , spreading to different lands, that additions are quickly seen- since they were only in a few in a certain area. Scholars also have many techniques to discern additions- such as differences in inks & hand-writing.
Read Romans chapter 10 in any Bible except the NWT; try to understand what point Paul is trying to make, and how the quotation of Joel in v. 13 serves his argument. When you get it, switch to the NWT and see what happens.What did you see "excercis faith" instead of "believe"? "Jehovah" instead of "LORD"? It seems the same to me- just easier to understand.
Mad