> Use PEN on a suitably large wall surface to sketch out map of the rooms, leaving enough space to detail what rooms have what, which ones are explored vs unexplored, ect. There are a lot of rooms after all to keep track of now.

Behold, your masterpiece.
If your arm was sore before, its practically falling off at this point. Might as well mark off the details for now, too.

You did not remember if the 3 rooms you were in prior to the discovery of the CREATURE had anything to the sides of them since that was already a little bit ago, so you left those boxes blank.
It is very important to note that this is being done with a PEN, and one with ink that takes very long to dry at that. You might be able to smudge away any old information for new stuff, but you really would rather not.
Hopefully the other PENS in the CHEST have better ink if you need to use them later. You could also potentially try using the WET PEN INK to stick pages of the NOTEBOOK to the wall, but that is probably stupid and will not work probably.