Unfortunately I can't help with HTML\CSS because I've touched that stuff a decade ago and I forgot most of it; from what I remember, it shouldn't be difficult to figure out.
Judging by your artwork it looks like you are drawing stylized characters most of the time so my guess is that you can't draw complex environments and foreshortening. Now your request makes more sense because perspective can be extremely difficult to handle. Just like you said if you'll perform only secondary tasks like cleaning and outlines you won't have to worry about styles so pipeline like that could work effectively.
If you use Photoshop your working format is .PSD which is important because your partner's software must support .PSD as well. As far as I know, that format is supported by most graphic software so it shouldn't be a problem. Technically it is also possible to use layered .TIFF, but I'm not sure how well it is handled by most applications.
If you use Illustrator as well, I recommend to stick to .SVG because that format is more widespread than .AI and can be edited in many programs without conversion.
Horror genre, be it a novel, a movie, a comic or a game is not about how much gore you can splat all over the place, how scary your monster is supposed to look like or how dark your environments are, it's about concept, atmosphere and pacing. Horror is one of the most challenging things to implement because concept, story, visuals and sound must work perfectly in unison to translate the proper mood. Judging by your writing samples my guess is that your horror stories are pretty much the same so perhaps it would be better for you to choose something else as a basis for further development. Horror is not something you can just write, it's something you must feel in order to do properly.
Speaking of it, Darkness Within 2 practically don't have any monsters or gore but it's still a great game because of its atmosphere and a vivid example of how pacing and style can deliver a great experience. Oh, and Lovecraft himself is literally in a game as well as tons of references to his works.
Overall, your proposal seems fit and my guess is that your field of work is mostly limited to urban fantasy with bits and pieces of superhero genre thrown in so you'll need someone who can depict modern urban environments and characters. As always, if you have any problems with architecture and perspective you can always use SketchUp for drafting so my advise still stand and I still recommend you to try implementing your own work instead of waiting for someone else to do it for you. It doesn't mean you should stop looking for a partner, it just means that the more you'll be able to do yourself the better.
I was planning on having one long piece
In my personal opinion, these laundry list comics are extremely inconvenient to read so I'd stick to regular format instead.