Are you serious? Your supposed examples of the powerlessness of the wealthy are full of holes.
It's obvious that, for a variety of reasons, at least some wealthy clearly prefer a corporate tax with a high headline rate but filled with complexity, deductions and loopholes rather than something lower, simpler and broader.
And, of course, the 50% income tax rate you cite isn't a tax on income from wealth - it's a tax on the income from labor. Perhaps you need to have a chat with Warren Buffett about his secretary.
As for the estate tax, in recent history the rate has been generally decreasing and the exemptions increasing (and most of the "increases" have been reductions of larger scheduled increases). There are also plenty of estates that don't want a full repeal - they gain more from the step-up basis than they lose to taxation above the exemption.
Finally, I think you radically overestimate the interest the truly wealthy have in leaving the US. US citizenship is still quite valuable and as long as they hold US assets (likely because of the breadth and depth of US investment options) they'll be dealing with some form of US taxes anyway.