@00DAD: the advice on how to handle the mother is sound. But I can't say I would advise handling the Elder the way you presented. You know as well as anyone on JWN that if she responded in any of those ways, the Elder will be able to find someone willing to point a finger at her and the family with a vague accusation of apostacy. If necessary, the Elder will find a second person who happened to "remember" instances of uncleanliness or apostacy.
If you and your mother are ready to exit on your own terms, do it at a meeting. Tell anyone who will listen that you're leaving and tell them why.
As for the PM, lay it out simple.
"The revelation during the recent case of Doe v. The Watchtower Society that the Organization HAS indeed instituted a policy that protects pedophiles and rapists within the congregation is cause for concern, and by understanding of Scripture, I am within my spiritual right to have doubts. I am not preaching my doubts to brothers in the congregation, nor have I disassociated myself from the Organization. Your attempts to slander me and ruin my connections within the congregation are scripturally unfounded.
I will be making note of your prejudiced accusations in the event rumors or gossip about my good standing should arise. I am a Christian first, but it gives you no scriptural grounds to make uninformed accusations to anyone, especially under the idea that because you wholeheartedly support policies that protect the wolves among the flock who would hurt Jehovah's children, so must I unflinchingly.
Should you feel the impulse to criticize me further, I ask that you follow scriptural procedure expected of all brothers in our Organization and come to me first to discuss your grievances so that your words do not wrongfully spark a debate among elders who would take your good standing over my tarnished reputation (made possible by your impatient, uninformed accusations) and see fit to clean me from our Christian congregation. Imagine if your words got a Christian wrongfully disfellowshipped. Left in Jehovah's hands, where would one bearing false witness fit into Paradise? You can no longer say you didn't know the severity of your impatience because you are being told now.
I feel you are teetering on the edge of the truth, and it's my responsibility as a Christian to let the elders know because you don't seem to be willing to tell them, and if I stay quiet, Jehovah says I am equally responsible for your sins.
With warm Christian love,
YOUR NAME HERE"
Or something to that effect. Discredit his accusation, take screen captures, warn him he is at fault now for false witnessing, and add the piss to his pants by reporting him. Use the Witness tactic of the Red Herring (change the subject of your faults to what it is he's done wrong).