I have my undergrad degree and am interested in pursuing my PhD. I honestly believe that this idea that academics are somehow opposed to genre fiction is outdated. Granted, I've interacted with a limited number of scholars. but the two newest English professors at my school specialized in crime literature and animated films. All of the professors I knew had at least one or two genre interests that they wrote about. In my mind, this assertion is the same with graphic novels (which I wrote a significant thesis on) and although traditionalist programs tend to look down on both genre and comics, there are tons of progressive programs that celebrate other kinds of literature- UC Berkeley comes to mind. If you look through faculty pages at the top programs, most of them have at least a few professors that specialize in some genre or another. So at least to your last question, I don't think that it's a publish or perish situation at all. In a post-Theory focused world, historical context and the way that these works, particularly horror and sci-fi, reflect cultural concerns is an extremely interesting area of study.
I've had a limited opportunity to read criticism of horror, but what I have read is certainly interesting, both on horror lit and horror film. Honestly, the target audience is most certainly other academics, largely because the techniques used in the analysis require study to make sense. An average reader doesn't know what Marxist critique is, much less how it applies to a given text. That isn't to say it doesn't bring something worthwhile to the discussion, but it's just not the same discussion the average reader is a part of. That probably comes off as the exact kind of Ivory Tower elitism that genre readers and writers alike despise, but I don't mean it in a condescending way. Criticism just doesn't apply for most people, since they read solely for enjoyment.