I'm writing this fully aware of how stupid I'll look once the last episode airs:
That little tidbit about the art exhibit when Marty was talking to his ex-wife got me intrigued. Odds on one of the paintings being of the Yellow King or something else that's related? My predictions:
1) The climax of ep 8 will involve Marty and/or Rust stumbling upon said (hypothetical) painting, not sure on the circumstances, connecting the dots and racing to stop her ritualistic rape and murder. They'll obviously be just barely too late, since I don't think a happy ending would fit the show. Season ends with Marty and Rust killing the people responsible since they didn't manage to flee the scene, Marty sobbing over his daughter's corpse and possibly committing suicide. Rust narrates the closing scenes, probably something about the f***ed up nature of humanity. Credits.
2) Maggie's dad is one of the bastards that Papa Tuttle sired way back when and is one of the hooded men on the tape. Surname isn't Tuttle or Childress so Rust and Marty don't figure it out until it's too late. Maybe they don't ever figure it out, and only the audience gets the reveal. Could do something like having him pop up briefly in the beginning of the episode, simply so that the audience gets a reminder of who he is and what he looks like. Then at the end, after a grief-stricken Marty offs himself, have a little flashback as Rust narrates to the actual night the snuff video was made. The men remove their hoods one at a time when the camera has stopped rolling after the video from ep 7 was shot. The last one just before the end credits is the father-in-law.
I've given this way too much thought.