It's called a provocation, i'm bisexual and i do gay/lesbian joke all the time not joking about it just make it worse...
Lust Epidemic is the first part of the story, Treasure of Nadia the seccond and this is the third part.
No but character of ToN does appear in the game, just like LE character appeared in ToN.
It's also the next part of LE/ToN storyline.