Comments, criticism (including flamebait and trolls), etc., are welcomed. I am not a "professional economist", just a nerd that's been thinking and reading, and I know that I've grossly simplified many things, but think that I've captured their essence. I've no problem with others proving me wrong, so long as they actually do so.
I think the part you're missing is the reason for the move from gold (or silver) backed currency to fiat currency. The reason wasn't because the "supply of goods and services outstripped the availability of money"; the reason was the boom-and-bust cycle. The idea was that by manipulating the money supply, the Federal Reserve would be able to soften and smooth the boom-and-bust cycle, making the "busts" much less severe. (It's no coincidence that the Federal Reserve was created shortly after the Panic of 1907, and subsequent reforms have happened after every "bust" since then [like the Great Depression].)
Now, there is no small debate about whether this manipulation of the money supply has actually done anything at all to quell the boom-and-bust cycle. Some have suggested that these boom-and-busts are inevitable, and by delaying when they happen through manipulation of the money supply, it simply makes the inevitable bust that much worse. (Personally I think it is possible to smooth out the bumps, but that requires minimizing the economic good times as well, which I think historically hasn't been a very popular Federal policy.)
Of course, there are also others who assert that the purported reason for fiat currency is a lie, and that the real reason behind fiat currency is to "print money" on demand, inflating the currency and enabling the government to pocket the difference--but when you look at the amount of revenue gained by "printing money" compared to the usual methods governments have of raising revenue (plain old-fashioned taxes), it seems unlikely that this is anything but a fringe benefit of fiat currency. In any case, I don't think there's any debate about at least the purported reason for the Federal Reserve and fiat money.