Two separate issues here
The false disk space issue you had before should be addressed in 1.15.0.659 which has just been released. See Plex Media Server
It is not mentioned in the list of fixes but the fix is there
The second issue is the iNotify maximum being reached. This is a linux system limit which you should be able to reconfigure to increase the maximum from the default . I think it is ulimit. But you can either search forums or web for how to increase it if you are not aware
