Definitely I second a suggestion for faster walk speed! Although, 90% of the issue is the really low framerate sadly - I suspect all those fire shaders around the map might be causing the issue!
EDIT: I can't seem to progress after getting into the attic, I see there's a couple craw-spaces around but you don't crouch quire enough to be able to squeeze through. Perhaps the crouching animation is tied to the framerate? That would explain, unless the demo ends here!