Thanks for this well detailed feedback.
1) Yes, it's on our roadmap.
2) It was/is a design choice, we aren't so familiar with using redis as a persistence store. The goal was to enabled people switch backends depending on what they're comfortable with.
3) Thanks for bringing this up, there are a ton of things we should document.
4) We're working on improving things from a security perspective.
On application-wide keys, we're considering making this configurable, so you can choose what works best for you, we only started with app-wide keys, next is endpoint-keys. :)
On public/private keypair, this is new to me as well! we haven't found anyone doing this in prod. But yes, I can see how this can be useful in specific environments, definitely something we'd like to support.