I feel so bad for you. Seriously that's gotta hurt. You said that most of your reviews were video ones. I didn't even know that you could upload video reviews onto Amazon. Never seen one myself. Have you also posted them on YouTube. If so, if you don't mind sharing your channel, I'd love to admire all the hard work you've done. Again, I'm so sorry this has happened to you. Seems insane to me. You'll probably have nightmares for a few weeks. I agree with everything you said. I mean I guess I can understand them taking down the ones that you stated you were given for free, but even those are already not as weighted as they are unverified purchases. Heck, they don't even show up when you're scrolling through the reviews unless you change the default filters (every time). It frustrates me too. Again I agree that I appreciate the meaningful reviews so much more than the dumb ones.
As far as them taking down your account... I'm not even going to say anything. That's just stupid and would (or at least should) never happen.
I will say that if Amazon loses their top review contributors, that will hurt them in some way or another - when you reach out to them there should be absolutely no doubt that all of your hard work is restored (other than the ones you received at a discounted price or for free, especially if you tell them that those were written before the rule change and that you tried to go back through and delete as many as possible). Good luck, you'll get through this.
The people that are falsely reporting you should have their privilegedes taken away, including selling their products - or at the very least a warning.
If they've got time to destroy your work, they've surely got time to make it right and forgive that all of it happened in the first place.