1) Sorry to be imprecise. I meant to have just one Posters/Presentations slot with all three posters cited in the same narrative space.
2) Yes, you could do that.
3) While a "patent pending" or a "patent" are worthy of their own space using Publications or Other, anything earlier in the pipeline, like a provisional patent, should be mentioned in an affiliated Employment or Research entry. You might potentially use your patent lawyer as the Contact.
4) Until it's accepted somewhere, I suggest leaving it off the application. If you feel compelled to include it anyway, it would be to report the experience of seeing an interesting case and preparing the case report after exploring the literature for similarities. Other or Teaching seem like good choices for a tag. Extracurricular or Artistic Endeavor (for writing) could work, too. The impact of the experience on adcomms would be far greater if you wait until a journal editor validates the article's merit by accepting it for publication. So consider saving it for Secondaries or update letters.
If you need more space to discuss this specific project, you could take it out from the current grouping and give it its own space.