So, as of right now I've also managed to get the latest version of the CRIWare SDK tools as well.
There's no way to convert USM to any other format 100% (vgmtoolbox tries, but produces corrupt video), same for ADX, etc.
My solution is a tad janky for this, I've basically loselessly screen captured the video from the included USM player. The results are perfectly acceptable, even when reencoding the files back into USM.
EDIT:
After a few hours of playing around, I've actually managed to decompile code for the game's scripts, meaning I can now directly edit the way events work, when sounds play, what sounds play, what messages get loaded, etc.
I'm probably going to look into this more for text editing purposes. Trying to find control codes, etc.
EDIT 2:
The function is embeded in the Lua enivironment in the main executable, so I won't be able to get anything.
However I managed to find (most) of the control flags used in the game, even a debug switch.
My next step is to try seeing if I can recompile the code and get it to work again, fingers crossed here.