Your post is great and i absorbed alot from it. The following are the points i am repeating again and again to memorize.
Both are durable. Neither gold nor cryptocurrencies "expire" in any meaningful way, like paper money does.
Both are fungible. Fungible currencies are ones where a specific unit can be replaced for any other. An ounce of gold is worth an ounce of gold once it is melted and purified. A Bitcoin is always worth whatever the market says Bitcoins are worth at the moment.
Both are scarce. There is a finite amount of gold on Earth. Likewise, the Bitcoin protocol stipulates a hard limit of 21 million BTC – the most that will ever exist.