All good and valid questions, and intelligent ones at that. Sounds like you did fine answering them, too. Better than I could. I don't think satoshi's coins are ever going to move and if they do, I see it as a founder's fee. Like a stock option almost.
Satoshi's founder fee (as you call it) is currently: $580,000,000 and perhaps a fraction of this if he dumped too fast, but out of a 9.3 billion dollar market cap that is a fair compensation. I totally agree with you! This technology will have a greater impact on the world than many other billionaires contributions to humanity.
However, my concern is if Bitcoin ever hits the trillion mark. We are talking some serious fire power/control on his end.
So let's say BTC hits a $1,000,000,000,000 (1 trillion) market cap and the current BTC in circulation is 19,000,000 (based on exponential difficulty projection in the hashrate). This puts the BTC price at $52,631 roughly and his net worth at 52.6 billion dollars. Which still, I think is fair considering Bill Gates is currently worth 75B.
This might sound crazy, but I do believe BTC has the ability to reach parity with the total value of the gold market and potentially exceed it (could take 1-2 decades) since use case/utility is obviously better (especially in this digital world we now live in).
The total gold market is currently 7.8 trillion, so for quick math let's just do 7.8 x 52.6 billion = 410 billion making Satoshi the richest man in the world by a significant margin.
However, if all these derivative bubbles start to meltdown (AND they will) we're talking some SERIOUS global wealth transfer into BTC and altcoins. This could potentially make Satoshi a trillionaire if you run the numbers. Is it still a fair founders fee? Perhaps, but kings couldn't fathom this type of power and on top of that he could act as a ghost in the matrix with complete control (since he's anonymous). You also don't know if it's one man, two men or a think tank or their intentions... bum bum bummmm!
If I was Satoshi I wouldn't touch the cold storage either until the entire world was dependent on my system and all infrastructure integrated into BTC. (IE. imagine the Google search algo going down for a month... people would shit their pants because global markets have built a dependence).
BUTTTTT that requires BTC to scale for the need/demand and right now... eesh! (we need to get on that!)
Lastly, I should mention that if this were to occur BTC would cross this Rubicon where people would stop pricing things in dollars, but rather BTC (dynamics of all markets would be turned on their heads). Makes the math way more difficult, but we could quantify it and say his net worth would be 45,000,000,000 4 bedroom 2b houses OR 1MM BTC... ROFL
This will help you visual what I'm talking about here: (if you haven't already seen it)
http://money.visualcapitalist.com/all-of-the-worlds-money-and-markets-in-one-visualization/