Generally you do not go back from an emulator on modern consoles, they are still very useful but not in the way you have started to head down.
Anyway for future reference you seem to have forced 16 bit unicode (or a subset of it) going into fixed length (albeit one with a very generous length) sections. That is quite nice actually.
You will need to figure out the compression format used by the game, decompress the file, figure out the full format (they are often the same but it has been known to change) and recompress it before inserting it back into the game. I have not really done any PS2 compression but it has enough RAM and CPU power that more or less anything could have been used. Though the sections do not match it seems they retain a level of readability which decreases at points and is interspersed with various numbers -- this would usually indicate something in the LZ family.
I usually suggest https://ece.uwaterloo.ca/~ece611/LempelZiv.pdf
as an intro the various common classes/types of compression.
The lazier way might be to make a cheat if the file always ends up in the same place in memory but go with the normal method first.