I'm thinking of doing something similar with my parents. What I'm going to do is write down a lot of the JW's main doctrines (paradise earth, 144.000, 1914 and other dates etc) and write down all the info I can about them. Also answers to any rebuttals that my parents might bring up. Some of the scriptural ones are -
Ephesians 4:4 - There is one body and one Spirit, just as you were called to one hope when you were called? One Lord, one faith, one baptism; one God and Father of all, who is over all and through all and in all.
Why would the name God gave to His people not be "Christians" since Acts 11:26 says, "The disciples were first called Christians in Antioch"? Why is the name "Jehovah's Witness" found nowhere in the New Testament, if that is God's divine name for His people under the new covenant? Why would God wait almost 2000 years to suddenly start using the name "Jehovah's Witness". Does this mean that first century Christians were not known as Jehovah's Witnesses"?
Since the Jehovah's Witness organization currently rejects most of the teachings of its founder Charles Taze Russell, and since they also reject "Judge" Rutherford's teachings, how can we be sure that in 25 more years, Jehovah's Witnesses won't also reject the current president, Milton G. Henschel, as they did Russell and Rutherford?
The NWT translates the Greek word "kyrios" as "Jehovah" more than 25 times in the New Testament (Mt 3:3, Lk 2:9, Jn 1:23, Acts 21:14, Rom 12:19, Col 1:10, 1Thess 5:2, 1Pet 1:25, Rev 4:8, etc.). Why is the word "Jehovah" translated when it does not appear in the Greek text? Why is the NWT not consistent in translating kyrios (kurion) as "Jehovah" in Rom 10:9, 1Cor 12:3, Phil 2:11, 2Thess 2:1, and Rev 22:21
The Watchtower Society teaches that the 144,000 of Rev 7:4 is to be taken literally. If chapter 7 of Revelation is to be taken literally, where then does the Bible say that the 144,000 will come from? (See Rev 7:5- 8).
If Jesus was executed on a torture stake, with both hands together over his head, why does Jn 20:25 say "...Unless I see in his hands the print of the nailS ...", indicating that there was more than one nail used for his hands?
Jesus uses the phrase "Truly I say to you, ..." over 50 times in the Bible. In the NWT, the comma is placed after the word "you" every time except in Lk 23:43, where the comma is placed after the word "today". Why is the comma placed after "today" instead of after "you" in this verse? If the translation of this phrase in Lk 23:43 was consistent with the translation of this phrase in all the other verses in which it appears, and the comma was placed after the word "you", how would it read?
In Rev 19:1, where does it say that the "great crowd" will be?
In Col 1:15-17, the NWT inserts the word "other" 4 times even though it is not in the original Greek (see Gr-Engl interlinear). Why is the word "other" inserted? How would these verses read if the word "other" had not been inserted?
If Jesus was executed on a torture stake, with both hands together over his head, instead of on a cross with both hands outstretched, why does Mt 27:37 say that the sign "This is Jesus the King of the Jews" was "posted above his HEAD" instead of being posted above his hands? How could it have been posted above his head if his arms were stretched out over his head?
Heb 11:16, in speaking about some of the faithful people of the Old Testament (Abel, Noah, Abraham, etc.) says, "But now they are reaching out for a better [place], that is, one belonging to heaven..." and, "... their God for he has made a city ready for them." The footnote on the word "city" refers to HEAVENLY Jerusalem of Heb 12:22 and Rev 21:2. How can this be since according to the teachings of the Watchtower Society, the only people who will go to heaven are the 144,000 spirit anointed who have been chosen from people who lived after Christ died?
Where does it state in the bible that the door to heaven shut in 1935?
Where does it mention in the bible anything about a great crowd living on a paradise earth?
Name one thing that the WTS has said would happen that has actually occurred (if 1914 is mentioned say that the bible students expected armageddon to happen and them all to be whisked to heaven in that year)
If they are always wrong and not inspired by God and their doctrines are unscriptural, why should we believe them?
I'm still working on stuff and possible questions that might be raised. I figure it's best to be prepared and play them at their own game with the bible. The ultimate would be if they read CofC & ISOCF. They are not even 'apostate' literature by the WTS own terms. Ray Franz says in the book that he's not trying to turn people away from the WTS or feed them his own personal doctrine. It's just his journey through the org and his experiences in it - people can judge for themselves what to do with that info.
Personally I don't think my parents will take everything onboard and quit but at least I can say I told them the WTS is bunk.
All the best, I hope the chat with your dad goes well.