Panasonic Let’s Note, SV7 or SZ7 I think. Japanese domestic notebook for enterprises

Try Syncthing with IgnoreDelete but note that it’s unrecommended. Maybe use Syncthing as an append-only store

It’s entirely possible. If the 2 domains are different, you should look into SNI routing using the TCP router instead of HTTP. With the tls.passthrough flag, encryption is kept intact until it reaches the second proxy.