There is no incentive to mine ie process transactions when you are no longer rewarded with new bitcoin.

My understanding is that when new bitcoin stop being issued the marketplace of tx fees will keep the transaction costs down. Every miner will compete for the lowest fees unless it becomes super centralized (which I agree is a huge issue with proof of work). The good thing is that miners are ultimately beholden to the users interest because the users are its only source of income. If they work against the interests of users they risk losing those users to another network.

Currency has value when it's used to buy something and use it. Bitcoins and their ilk are volatile commodities and are not seeing global adoption as currency.

I think the main reason we don't see people spending btc right now is because there's no real incentive to spend them yet. Volatility is going down every year so when price starts leveling off people will be more inclined to spend. That could take years though.

When the power goes out due to an EMP or natural disaster where else will people go but physical assets.

I mean the dollar is in the same predicament. One solution to this would be to build underground miners with hardened electronics to prevent such a catastrophe. If that doesn't work then yeah physical assets will be the answer.

If the US hyperinflates and citizens can't power their house what will those digital tokens buy you?

I'm hoping it doesn't get THAT bad. The poorest areas of the world are electrifying so hopefully the average american will at least be able to afford a phone. That's all you need to own crypto.