I have to say, this was a treat for me and it just looked super eerie, creepy, well crafted and the design for the wagon was just great. I liked this a lot. This is excellent game for the Jam and I can't wait to see the results for your game.
The strongest parts of the game were sound design and environments. The cutscene in the beginning was very cinematic and I though I was watching a movie, fantastic job. The P.T. like gameplay, at first was somewhat blending with the environment, although couple of loops I think could have been taken out, maybe 3-4 loops. When the music started playing and the environment acted the way it did - now that's when I felt unsettled, disturbed and that's the reason the game fully qualifies and makes it on top for me, personally.
I do hope you can continue working on this after the Jam and can't wait for other projects you might be doing. You have amazing potential for making this type of games. Amazing Job!