Re your 1. "PoW as an anti-spam measure":

I'm working on PoW WoW, a distributed marketplace for event PoW. Can be used by mobile clients who can't afford to mine themselves, allows miners to join or leave at will, and be paid non-custodially over LN.

It has Rust libraries for clients and providers, but I can add bindings for other languages too.

nostr:note1qqqqqqpphaqu6jxayvczlajf3h7s57dvzwcsr9cp83lxuh2nd6dq29r9dd