Horror almost definitely includes gore above and beyond the point that is necessary (people will die in spy movies, sure, but usually not horribly). Worm has enough that turned me off reading it for a month or so (Killington or the S9 in general).
You won't find horror in most popular thriller/conspiracy kind of novels, it's definitely distinct even if the lines can blur occasionally.
Torture-porn isnt strictly horror, though; Iirc current detective stories are full of it.
Imo torture-porn isnt even a good idea in horror. Has to do with revulsion, not fear.