Is the Guild Leader the only person allowed to unlock or lock the Guild Stronghold. This seems a problem if hosting a public event and then wanting to shut it down when finished. I don't see an option anywhere to allow Officers this ability or have I missed it somewhere?

As far as I can tell yes. The GM is the only person that can toggle the guild stronghold from public to private and vise versa. Also even if you toggle back to private with the people in the stronghold (or logged out in the stronghold) they will not be auto removed from the stronghold. They will either need to leave of their own free will or the GM will need to manualy kick each one from the ship or stronghold when they are logged in.