Very familiar with this subject.
I left in 2001, and my mother lived faithful until her passing in 2010 at 98 1/2. One of the things I resented and still resent is because of the WBTS, she was so so so worried about my imminent destruction. She really wanted to save me. I avoided ALL discussions about da troof. Whenever she wanted to share something I just said "that's great!" "how nice" or such in a manner that conveyed a response but no discussion. When she offered a magazine I acted happy to see it. Change the subject. It's pretty easy when they are that old. I played the "christian" card when she started misbehaving. "Hmmm...WWJD." Seriously. It stopped her.
My feeling is I could not change her, and the religion gave her something she needed. I would reassure her things will be fine and not to worry. She wrote me some crazy letters trying to save me that to this day brings tears to my eyes because I knew it took a lot of thought and energy, and worry on her part. I hate the GD WBTS. Needless worry. Sigh.
I had to accept the fact that she was probably co-dependent on the society, and if it wasn't this, it would have been somebody else. They just were the ones that came knockin. I wish it would have been different, but it wasn't.
My advice is to not engage. He will continue to try to save you. Keep the peace. And this situation with that generation not being too attached to grandkids, it seems a bit common with the WBTS. Weird and frustrating I know, but it is what it is. Whenever he brings up any congregation or WT news, just act happy and complementary about it. 5 baptised? "That's wonderful!" and change the subject even though you want to barf. There always is a bit of anxiety around it...but concentrate on keeping the exchange peaceful and be in control. It seems to end the conversation quickly for some reason.