No, at least the last time Warren make this proposal, he was talking about unearned income, too.
Of course, Warren knows very well that dividends and capital gains have already been taxed once at the corporate level before distribution to shareholders. That's just one reason for the reduced tax rates.
What Warren really wants is to raise the barrier to you getting wealthy, by making it more expensive to accumulate and reinvest investment income. It's easier to stay on top of the hill if you spray water on the sides and make it slippery for everyone trying to climb the hill.
Yep. You are correct, he is also asking for a minimum tax that everyone pays. Also correct that his motivation is to create a barrier so no one else can grow enough wealth to compete with him and his company heirs. I am not sure how this guy became the world expert on tax policy, as if he is not a direct beneficiary.