Rent a bitch a horse, she will ride for a day, buy a bitch a horse she will ride you everyday - Margaret Thatcher.

If you are only accessing the services while connected to tailscale using the tailscale admin console you can add a nameserver, and then point that to a local DNS resolver. The local resolver can point the URL you want to the IP with the ports you want. I don’t know if Synology has DNS resolving apps but that might be an option, otherwise you could run pihole or something similar to achieve this.