2) The economics of providing for network security when block inclusion is free and inflation has dwindled
For (2), I feel like there's a factor I never see mentioned. In the short run (12+ years), the block rewards are more than enough to incentivize mining, especially as we're moving to a world where the variable cost (electricity) of mining is plummeting. Over that same timeframe, the cost of ASICs should also plummet to the marginal cost of production at the same time Moore's law is increasing their power. Hashing power is going to be cheap. Very cheap.
Hashing power being cheap is not relevant to the security of the network since it would be equally cheap to an attacker. It's the total amount of resources employed by honest miners relative to those of an eventual attacker that actually matter.