I don't think there are any questions that could not be dealt with to the self-satisfaction of an informed JW.
I do think it's worth challenging JWs as it may have a cumulative effect over time but there are no magic bullets. If a JW is reasonable it's probably better to try to reach the authentic self behind the cultish facade.
It really doesn't seem right to any decent human being to shun a family member because they have different beliefs about supernatural things. It isn't right that a child should die for lack of a transfusion. It can't be a moral good that they pray every day for the destruction of 99.999% of the earth's population, and so on.
I sometimes adopt the role of sympathetic confessor and watch their discomfort.
Of course they won't agree with you in public but you might trigger an internal struggle.