I would question the comparisons you have drawn between biblical characters and the JW organization on the following basis:
Moses, Aaron, the Israelite kings both good and the bad, as well as the individual Israelites themselves were God's chosen people because of promises made to their father and ancestor, Abraham. God would correct things when their conduct became excessively bad, but until those promises made to Abraham were fulfilled, they continued to be His people regardless of how bad they acted.
Jehovah's Witnesses claim to be "God's people" today not because of a hereditary promise of any kind but because of their conduct. In the context of what they teach and what they do, this conduct is alleged to have been so remarkable that Christ chose the JW organization in 1919 as the one true "Faithful and wise steward" and appointed them over all his belongings. Therefore conduct is everything
When you draw a comparison between King David, Manaasah, etc. you are presupposing that the same basis for overlooking the excessively bad conduct of past organizations still exists today when in fact it does not. Jesus clearly indicated at Matthew 24 and Luke 12 that the slave would be rewarded or punished based upon conduct and conduct alone.
The JW organization has willingly and voluntarily applied that parable to themselves. Therefore neither you nor they have much basis for appealing to past hereditary systems in defense of today's bad conduct.
I'm not trying to be mean It's just that the JW's themselves have pulled the rug out from under the whole idea