I'm sorry to hear of your suffering. You tried your very best to be a good partner, mother and Christian. You did what you thought was the right thing at the time, and that's all we can ever do but, of course, in the Watchtower trying your best is never good enough...and the meek, the gentle, those without ego feel it the most and become depressed when they can't be superwoman and fix the whole world!!
Woman without a voice is a good title because really no woman has a voice in Watchtower, except through her husband, it's like going back to those cruel ancient societies that had no use for women except to be slaves or produce babies. Why do we tolerate it? Usually because we are attracted to the loving message of Jesus, yet for all their bluster Watchtower has nothing of that. Sadly, even if they are kind men, elders MUST be company 'whips' first and foremost...and like parliament if they fail in that task the 'whip' is taken away from them and they are cast out.
I don't know what to suggest about your sister and husband except if you wish to help them, especially your husband who seems, if I read you right, to be almost bullied, never state facts but use the Socratic method of posing questions, such as: I was wondering why the Isrealites held their courts at the city gates, so nothing would be hidden from all men....I wonder why does the bible say we MUST have JCs in secret with 3 elders? What if a bible study asks to know where it says that in the Bible ? etc etc
Anyway I'm glad that you have come here and I'm sure many of us can relate.I too had an abusive first husband who would drink and throw me and my baby son out but was told the answer was pray and go in service more!