"They are fearfully conscious that Yahweh is about to slaughter billions."
Ah yes, but those are supposed to be those that rejected the JW message. It's much more difficult to explain away those who happened to belong to the wrong tribe in biblical "history". There's no official JW doctrine to explain away the capriciousness of who dies in that time period or the blatant cruelty. Slavery, killing of children/babies in conquest, and being forced to marry your rapist don't sit well with modern ethics. There will be JW diehards who will do mental gymnastics to find it somehow "acceptable", but it's a weak point in the JW bible-as-literal-history perspective.
*I should probably mention that trying to convert a JW to a different religion is virtually impossible (if that's what you're attempting). When JW beliefs are dismantled... belief in the Bible/God often crashes and burns.