If you can superimpose a blocker over real-world ads, you can superimpose ads onto plain walls too

Depends on your use case. If you’re just looking to expose services and are ok having them publicly accessible, there’s Cloudflare Tunnel, or you can run WireGuard on a cheap VPS

A lot of work has gone into making floating point numbers efficient and they cover 99% of use cases. In the rare case you really need perfect fractional accuracy, it’s not that difficult to implement as a pair of integers.