I uninstalled it last night. No idea why that file got so big, or if it was the cause of my problems of late. There were quite a few:
Hard drive was suddenly filling up. Tech Tool started announcing the start-up disk was getting below 15% and lower, even after I deleted 100GB of files (not the KAV file, other things). After those stopped the system was telling me my drive was full, while the finder showed 100GB+ free space.
External drives wouldn't cleanly dismount (icon would remain dimmed out, system would chide me for disconnect them)
System hangs on restart
I've got two other threads running on these issues.
https://discussions.apple.com/thread/3132632?answerId=15941378022#15941378022
So far since restarting from SafeMode I haven't gotten any disk full warnings (though it did hang on restart), though now I'm up to 250GB+ free space since deleting the KAV file.