Thanks for your analysis Hepatizon! It was about what I was expecting.
However, I don't think this is quite correct.
For one thing, the way the blocks are currently set up, it takes linear time with respect to the total number of transactions (and I think more than that in memory) to verify one transaction. So after 10 years of bitcoin, you need to either go through all 10 years worth of transactions, or have a snapshot of all the account balances of every user ever and work from there.
It appears that each new transaction has direct links to each prior transaction being used as an input. To validate a transaction you only need to validate the immediate dependancies. You don't need to validate those dependancies' dependancies as they were previously validated as part of the block chain. That means closer to constant time rather than linear.
I'm new though so I could be reading it wrong. Please correct me if I did.
The rest of your critique seems well analyzed and a bit frightening. Thanks again!