I've adjusted all my volume levels to 90 via editing build.prop, save and exit, reboot into TWRP, clearing cache/dalvik cache and booting llikenormal...works great.
OP - I'd like to know how to get surround sound to work as well. I've unzipped your file and found the mixer_paths.xml. Do I just copy and paste everything from the Play Scenario into my current mixer_paths.xml since it seems there a few different lines of code on here that aren't on mine?