SAHARA, very interesting story, your gut feel has been pretty good. It seems that you have been fairly accommodating and non judgemental about your wife's JW family. From their point of view you were only ever acceptable company while you were
a) willing to accept occasional witnessing (magazines left around) b) they could count their time on you c) it was a show for your wife on what happy families you'd all be in the truth d) a potential JW.
Stopping that sneaky and rather dishonest method of studying with your child would have, as you said, made you an opposer in their eyes. No need to keep up the pretence of being nice to you, they'd rather punish you and make you feel their disapproval.
Your wife seems to prefer to avoid confrontations and is happier taking the path of least resistance, or rather the path that least offends people. I wonder if your wife tells her family how irregular she is at meetings. The fact she is irregular shows she has issues with it. If she does ever discuss those issues or her family - listen, listen, listen and ask the odd question that doesn't require a response but will get her to think.
MMXIV