Here's a book that I found really helpful when I was studying/deciding whether to return to the JW's or not:
Answering Jehovah's Witnesses (by David Reed) - he shows a number of the scriptures that JW's use to support their belief, then shows how these have been taken from context, etc. This book was really good - every scripture that I had been taught as a JW to support my beliefs was in there!!
It's not a very long book - I read it in about 2 days.
Another good book is.. "What you need to know about Jehovah's Witnesses" This book has a lot of good scriptural references in it.
I suggest that you leave the JW history out of your conversation. Any good JW will tell you that because of "New Light" the doctrine can and will change. If you really want to help this person get out of the bOrg, you need to do it lovingly. Approach this person in a kind manner and simply ASK questions...when a question is answered with scripture and you dont agree with the interpretation...simply read the scriptures before and after the reference in question (to establish context). Point out to the JW that you believe that their scripture is taken out of context...but dont argue...just agree to disagree. What you really want is to get them thinking about their beliefs and why they think that way. There is a wonderful slide show on Freeminds.org that poses alot of questions the witnesses have a tough time answering...check this out if you havent already... http://www.watchtowernews.org/howto/sld001.htm