I've only ever gone to two fan events that were limited to one show - Star Trek in 1978 (an afternoon event with George Takei, in Calgary) and Doctor Who in the late '80s, at the Spokane PBS station when Sylvester McCoy was touring across the US after having taken over the role from Colin Baker. The rest of the events I've been to have been conventions where the guests have been authors, artists, editors, university professors, people from the local planetarium, and even Phil Currie, who runs the Royal Tyrrell Museum of Paleontology in Drumheller. No actors. These conventions had a wonderfully eclectic mix of people and guests, with many common interests. You could indeed have "given away" a Xena book while also selling your ST books. There are some extremely enthusiastic Xena fans in this area, even this many years after the show ended; one friend of mine started writing a fanfic crossover of Xena & Deep Space Nine!
Oh, most cons are not so specialized, I agree. I was mostly thinking of some Creation cons I attended back in the day. At Shore Leave a few weeks back, I was signing everything from Star Trek to Warehouse 13 to Iron Man and beyond.
As for Vulcan dating etiquette, it's worth remembering that Spock in not
a typical Vulcan engaged in a typical Vulcan relationship. If Spock wanted to adhere to strictly Vulcan standards, he would have just entered the Vulcan Science Academy as expected, instead of joining Starfleet. He has a lot of Amanda in him, maybe even more so than in the original iteration. And I imagine that his relationship with Uhura would be even more "human" than his parents' marriage, since Sarek was a full Vulcan raised entirely by Vulcans and less likely to overcome his upbringing.
NuSpock may even feel that he is honoring the memory of his martyred mother by allowing himself to be more "human" with Uhura this time around . . ..