It's not a bad demo but then again it feels misplaced since all of the pieces aren't put together yet.
To explain what I have said; Since the full game is not out, the symbolism shown in the objects isn't understandable, especially to those who don't actually look to see how this relates to another game you are making.
It's overall an okay demo compared to what I've seen and I do like how you use the objects to tell some of the story. I know it must have been a small time for you to have worked on this since you're working on a much bigger scale project- which I congratulate you on. :D
What the demo itself needs is a little more editing when it comes to grammar. Some mistakes were made but they weren't very apparent. I do think that this would be a good game for people to look for and figure out that not only did you make a full game but also a demo which was a prequel to it.
When it comes to making your big release, I have played and seen many games in the horror genre that either flop or are for profit. I'm sure that you're doing this for better reasons than those though. If you're going to label a price on it- if you really want people to feel that it was worth it- take into consideration the length of it and the work put in. I have never released a game myself so I'm sorry if I sound like a crazy critic right now. I've just had it with people making a 30 minute game and sell it on Steam for $10.00. No joke, there are plenty that do that or simply use mazes or key hunts to pad the gameplay length.
I wish you the best with your game and good luck with it! I'll be sure to watch for it!