The protagonists of the movie are serial killers, but they do it for god. Not anti-gay, just pro-family (despite gay families becoming more common. For now, for those who can’t live as out bisexuals or who can’t have all the flavors of love in their lives that they wish for, romance novels will have to be the next best thing. Find resources that are public. _dreamships_ and _dreaming metal_ are two that come to mind.
The rule of thumb
Bisexual character lesbian romance writing. 1992 ish without checking. Get yourself out of your comfort zone, stretch those writing muscles in new ways. Just a curious writer to another is your story one of the ones where everyone is gay. They are bad people because they are bad people.
@eadoin-grim: sounds like it would be a sad but unfortunately realistic story. Half the time, the previous characterization of these people rides the express train to hell.