Finally, parlamentarians selected by sortition would be less vulnerable to corruption.

Not so sure about that. If you're a billionaire it's possibly not so hard to buy off a few hundred people who are used to an average income - even if they're on an MP pay scale. (Especially if they're civil servants.)

And you still have other issues. The problem is not just about votes in parliament, but about public influence in general. That includes media monopolies (q.v. Murdoch), universities (q.v. Chicago school) and think tanks (q.v. pretty much everyone and everything in the US.)

Put simply, you need to change or remove entire technologies of persuasion and political distortion to get a useful result.

Votes are the end of the persuasion process, not the root cause.