Operating system locale support will usually account for the time offset associated with a given locale and allow for proper translation to and from UTC. In practice, it makes little difference if all clients share the same offset, however if there are clients with different locales accessing the same NASLite-2 server, then a proper UTC setting becomes significant.
In theory, there is absolutely nothing dangerous in setting a gateway for your NASLite-2 server, provided there is a clear understanding of what you are trying to achieve. If you are operating behind a firewall as you are describing, then you are correct in questioning the “danger” of a gateway. In short, if your LAN uses non-routable IPs and your firewall is not forwarding any specific ports to your NASLite-2 server, then there is no way for an outside request to reach the server.
