The harder the test to get in, the better. Maybe even a non-refundable 50+$ fee. I would give a lot to have a single space on Earth where mere popularity is not the metric of correctness.
As for monetary fees - demographic skew aside, that would significantly reduce the overall user population the more you charge, so a malicious actor would need correspondingly fewer sock-puppets to create the appearance of X% of the population saying Y, limiting its effectiveness as a deterrent. Amplifying minority views by a large factor or seeding new claims/statements doesn't require that many unique accounts in the first place.
You lost me. If some context was in there (as in "the current fundamental problem on my known platforms"), then everything else you said would follow. But there must be a way to do better.
I can personally think of many tactics currently unused by any social platform -- all of which would need testing to verify their efficacy -- but they leave the question open none-the-less.