We go three nights (though we are usually on a Sunday, Wednesday, Thursday schedule in October), and we really like it that way. We also have Express Passes. The first night we go through each house, the first show, and a couple rides (Mummy and Gringotts). The second night we go through each house, the second show (when there is a second show), and a couple rides. Then on the third night, we decide what we want to do: all houses or just favorite houses; one, both, or neither shows; and a couple rides. This plan works great for us! If we lived in Orlando, we would save up for the Ultimate Passes with Express and wear them out.
As for the blood and gore, yes there will be some. I except the House of 1000 Corpses house to by far have the most blood and gore. The other IPs (Stranger Things, Ghostbusters, Universal Monsters, Killer Klowns from Outer Space, and Us), I wouldn't think those would have a lot of blood and gore. Who knows about the original concept houses (Yeti, Depths of Fear, Graveyard Games, Nightingales), but my guess is that Nightingales might be blood and gore. The others, I wouldn't expect too much gore just spooky, thematic houses.
Based on what you've said, I really think you will have a great time. With three nights with express, you can try them all the first night and then skip the ones that you don't like on the second and third nights. Remember you also have five scare zones to enjoy as well, and those haven't been overly graphic the last several years.
Since you specifically said "spooky theming," that is another sign that you would enjoy
HHN. The set, costume, and make-up designers are really top-notch and make the houses and zones really distinct and thematic. It's really something to experience.