I think you accomplished the goals lined out in your Recommended Play section of "Lighthearted Horror".
I'm not sure if all the text was intended to be italicized and there's a few sections that stand out as un-italicized VS the rest of the page (excluding stat blocks), like pages 3, 10, and 15. I liked the illustrations you included and the layout really captures the feeling of hand-written notes or an ancient document.
Salt water draining negative energy from Undead was an interesting idea, especially given the monsters and the setting of a boat. I loved the Passenger Motivations table and the Ship's Manifest and the Passenger Quarters and Travel Trunks tables - these are useful even outside the context of this adventure, great stuff.