Tell your Uncle you have no desire to prove JW beliefs wrong, your only hope is for him to restore your faith and prove these things right. You have failed on your own and perhaps he can help.
Stick to one thing only Cyberjesus is right, he cannot be reasoned with and he won't want to hear what you have to say, by prolonging the conversation you dig yourself in deeper and are heading for JC.
If 607 is where you want to go then keep evidence to trusted archeologists say this is what you don't understand. If the premise is wrong the conclusion is wrong. State you have found no source outside the society that agrees with the 607 date. Please if he can find the trusted source that the society used to establish the 607 date then you would be so relieved.
Leave it at that. Keep the tone light and sincere, keep the meeting short. If he tries to cover other topics and ask other questions about faith tell him you are grateful for his concern and really it is this issue that is causing you a little concern and really he can help you best by resolving this small point. Don't get distracted to other points as he will use them as a stick to beat you with later.
Use your own diversions e.g. how is his family doing? Is he enjoying his work? Earthquakes etc.
Also make sure that you set the time frame e.g. I am glad you came but I can only talk for 30 minutes as I have to be somewhere else at whatever time. This way he can't camp on the sofa.
I wish you luck.