You left out Bitcoin as a vehicle for speculation. As you noted at the start in comparing it to gold, Bitcoin is an asset. Like any asset, it is subject to speculation. That makes it no more ‘stable’ as a store of value — which seems to me to be your primary concern — than any other asset.

Like any asset, given the right circumstances (i.e. parties to an exchange agreeing to accept it as such) Bitcoin can be used for purchases. That does not make it — or any cryto’currency’ ‘backed’ by it — a substitute for ‘fiat money’. (To my mind such ‘currencies’ suggest the extended chains of dependent equities that provided fuel for stock markets in the 20’s — and which compounded the magnitude of those markets’ collective collapse.)

People use “fiat money” when they mean “legal tender,” but in doing so they fail to capture — or even see — the difference that difference in terminology relates. As applied to money, ‘fiat’ is often used to connote (if it is not intended as a synonym for) ‘ersatz’. ‘Fiat money’ is legal tender, that which the community as a whole, through its institutions of government, has determined will be accepted for paying taxes and, significantly for your thesis, must be accepted by banks for repayment of loans.

Yes, nations’ legal tenders can also be used for speculation. That does nothing to make the case for Bitcoin intrinsically stronger.

Finally, to assert that Bitcoin is uniquely invulnerable to systemic catastrophes is just plain false. It can be hacked. Anything digital can be, and will be especially vulnerable as quantum computing comes along. With its vast consumption of electricity, Bitcoin can actually threaten the grids on which all electronics depend (especially in more materially vulnerable nations).

Personally, I have no reason to promote or denigrate Bitcoin (or any other ‘virtual’ anything) per se. I do think the proponents of anything should be very careful to avoid any misrepresentations in making their cases.