do you remember which names of the devouts are the ones showing with the black screen? Or do you mean you tried all of them?
As for west of the Dryad tree, there should be two more enemy encounters - an elven archer and a llorona where there's bodies of water. For the guy in hiding, you'll find him in the map below the Thessila one, hiding in a secret spot near the mountains. And Fiona will be available in the future!
I've tried Atris, Gwyn, Teleri, Savannah, and Merile and each went though all the fun stuff normally, but then it would do a black screen. For whatever reason, it doesn't want to show the "you have completed day X" if I have a bedmate at the shrine. Green lamia at her cave it works properly.
I haven't run across those yet, I wonder why? Do I need to trigger something to cause them to show up, or are the RNG gods annoyed with me? (Wouldn't be surprised if it was just the latter!) Thanks for telling me about where the guy was hiding, I was going "this is one of those easy clues that I'm missing, isn't it??" Being able to flirt with Fiona in the future is definitely a WOOHOO!
Edit to add something, I found the secret shrine, but both Enter and Don't enter have the same response, can't enter. Has this not been implemented yet or is this a bug?