Reasonable points. The $100B figure was essentially pulled out of thin air. That's pretty much the only way we can approach this question, for the moment, anyway.
Not sure I can agree with you on the valuation of the cash, though. For investors, a company's cash assets (and all of their other assets, liquid or otherwise) are little more than balance sheet abstractions unless the cash is used to return equity either in the form of dividends or buybacks. Investors have no access to it any other way.
Cash adds to a company's market value (and debt subtracts from it) and can be used as leverage but only if it were to be bought out entirely by another company. Apple isn't a takeover target though and short of it becomings one (highly unlikely) that cash might as well be on Mars as far as investors are concerned. What it represents to investors is the tantalizing possibility of equity return that the company may or may not provide. How does the market value that? Not so readily.
What this really brings up is the value and purpose of a tax holiday. Moving retained earnings from overseas to the U.S. does nothing if it isn't used for some purpose here that it could not be used for if it was held outside the country. Ideally it is put to work on capital investment, but I think we all know Apple doesn't have the sorts of opportunities that would soak up tens of billions in capital. The only other use is equity return to stockholders, which serves mainly to comfort the already comfortable. I would not refuse the money obviously but I can also see that it's smoke-and-mirrors economics if it's sold as anything but yet another round of trickle-down. In practice this is a great strategy for further enriching the already rich and a terrible way to benefit anyone else.