Nice, that guide seems to have explained pretty much everything that I've missed; such as the Pentagon Valve, the use of the rainbow potion, the lavender flower location, giving the firefly jar to the girl, about half of the coins, the flat screwdriver, etc.
However, there are a few things that I found that you could add:
1. You would also keep the Bag of Chips after the Forest Maze, and I remember using the chips instead of a bucket of water to get rid of the plant.
2. Although unnecessary, the Square Valve can be used as a Diamond and vice versa. (Seems more obvious than using the Star Valve for the Pentagon slot)
3. In the Painting Lady Room, you could actually use the Lighter or the Knife to burn or stab the painting. Although I would expect it to have prevented the chase scene or made the Painting Lady chase slower/easier, instead it still triggers the same chase but without giving you the eyeball.
+. Although this is likely a bug, I found that you only need at least 1 Jar of Paint to obtain the Sketchbook. Any Jar of Paint (Red, Yellow, Blue) will be taken from the inventory, but the remaining Jar (whether empty or filled with water (or maybe pigment)) will be kept in the inventory.
Also, I haven't tried this yet, but I heard that you could give the "Fish?" from Alba to the Shadow Girl.
Finally, other than the Number 375 ticket (which is probably for the full Chapter 1) and the Fish that I mentioned, what about the Bucket found in the Facility?