FreedomFrog,
I'll tell you up front that unless you have Jesus himself come down and tell you parents that JW is not the right religion they'll never beleive it. I've had the same problem with my family for years now. I'll detail some of the items that I've found in my textual criticism studies, but first let me say that you'll need to find a common ground with your parents outside of religion if you expect to have a relationship with them in the future. I'm sure that you still hold dear the values (outside of religous values) they've taught you growing up and it's those things that you both can celebrate.
Most of my research has been on the early christian church using non-JW literature and the historical record. This includes studying ancient manuscripts to find out what the original documents said.
Initially, here is a thought on the "inspiration" proof of the NT. We don't have the original documents so we have no idea what Jesus said. We don't even have a copy of a copy. The oldest know manuscript is from the late 3rd century. So, if God took the time to provide the miracle of inspiring the NT, whey didn't he provide the miracle of having it preserved down to our day?
Additionally, take out the New World Translation bible (large print) and look at all the manuscripts used to put that copy together. Then, take a look at different scriptures and see how they were put together. For example, take a look at Luke 22:39-46. Jesus is on the Mt Olives and as the disciples are praying he prays to God and then is arrested. There are four things wrong with this event. One, notice from the footnote that verses 43 and 44 weren't in the early manucripts but in later ones. Second, this is only time in Luke's writings where Jesus is in agony. If you look at Luke's passion narrative Jesus is pretty calm and collective and dies giving his life to God. Third, this is the only place in all of Lukes writings that and Angel appears and has nothing to say. This is a little wierd. Lastly look at the composition of the event. Jesus tells the desciples to pray, withdraws to pray himself, Is in agony, comes back to the desciples, and tells them to pray again. This composition is called "chiasumus" and was a litterary style used during that time. If you see the first verse (40) correspondes to the last (45) the second to the second to last, and so on. It is meant to draw attention to a central theme. Added verses change the theme from Jesus saying "your will be done" to Jesus in agony sweating blood. Doing this changes the meaning of the whole event, which would be changing the gospel. You find looking at the historical record that Jesus sweating blood was added in later centeries by scribes trying to combat Docetism which was an early christian belief that Jesus was not human (flesh and blood) but divine and only appeared to the disciples.
My point with this is that JW's like to take multiple sources and and combine them into one story. The "Greatest Teacher" book details the event of Jesus sweating blood and provides it as historical fact. When this isn't true. They combine events from all the gospels as one coherent truth when in fact their creating a new gospel. If you take the four books individually and look at them they each have a different story to tell. Mark's (the first gospel) theme, deals with a human Jesus that has emotion and doesn't want to die "why have you forsaken me?". Luke, on the other hand portrays Jesus and calm and collected and never shows any emotion and even dies saying that he gives his soul to God. Which one happened? They both couldnt have but the JW's say they did.
There are many other examples I could detail if you would like: differences in the birth narritives and the passion narritives, how the early chruch treated woman (there were woman bishops), the history of how the 27 books became fixed, even inaccuracies with the memorial arrangement (Jesus never said to "keep doing this in rememberance of me", that was first said by Paul (1 Corinthians) and added to Luke by later scribes).
In conclution, there are more changes/versions of the NT than there are words in the NT.
I hope some of this helps. I wouldn't bother trying to prove them wrong. JFK once said that "reason does not appeal to unreasonable men" and this is definitely true. If you go in trying to prove them wrong they will just put up their defenses and end up leaving angry.
