You aren't on the witness stand and you are under no obligation to answer their questions or justify yourself to them.
You can try the broken record assertiveness technique.
No matter what they ask you or try to lay on you, you can say, "I appreciate your concern, but I prefer not to discuss that subject."
Them: "How much field service are you getting in these days?"
You: "I appreciate your concern, but I prefer not to discuss that subject."
Them: "Why, what's wrong?"
You: "I appreciate your concern, but I prefer not to discuss that subject."
Them: "The end is just around the corner. It's important for us to be actively serving Jehovah and his organization."
You: "I appreciate your concern, but I prefer not to discuss that subject."
Them: "You're not listening to apostates, are you?"
You: "I appreciate your concern, but I prefer not to discuss that subject."
You can combine that with the fogging technique. You agree with them and then go back to your broken record.
Them: "I'm really worried about you. If you're not out in service and attending meetings you will be wiped out if Armageddon hits."
You: "You may be right, and I appreciate your concern, but I prefer not to discuss that subject."
Them: "Why do you keep saying that?"
You: "Because I appreciate your concern, but I prefer not to discuss that subject."
Them: "I feel insulted!"
You: "I'm sorry you feel insulted and I appreciate your concern, but I prefer not to discuss that subject."
Them: "I think after all I've done for you that you owe me a better explanation than that!"
You: "I'm sure you do, and I appreciate your concern, but I prefer not to discuss that subject."
Them: "I don't like this. I may take this up with your elders."
You: "That's up to you, and I appreciate your concern, but I prefer not to discuss that subject."