I saw this movie sometime in the early eighties, I think. I’m not sure if the man in the glass case was being tortured or sick. I always thought the movie was Dune, but having recently seen it as an adult I didn’t see that part. Could I have seen a director’s or extended cut in the eighties? Could it be the Thing?
Is it possible you’re misremembering the part about him being in a glass tank? The rest of your description sounds like “Hellraiser.” There’s a skinless man hiding in an attic convincing his former lover to bring him victims so he can become whole again.