Brian,
Unfortunately, you can't use DFM to alert you when a host agent's file system fills-up. The FSRM feature doesn't specifically capture the file system "percent full" as part of its counters. There are a number of open systems host monitoring utilities that suppy that functionality (Nagios, etc...) and DFM isn't trying to reinvent that wheel.
ONTAP and DFM cannot peek into a LUN and interpret the file system, so they can't tell you how full it is. Only the host O/S that is writing to the LUN knows that fact. So that's why you don't see any events or alarms related to "LUN full".
However, you could script your own alarm here. When used with the File SRM feature, the NetApp host agent reports how many bytes of data are in the entire path (dirSizeTotal). You could divide this number by the total capacity of the file system to calculate the percent-full. If its over a certain amount, you could e-mail yourself.
To get the total bytes in a path, use the following command from the DFM server CLI:
# dfm srm dir details <FSRM PATH>
# dfm srm dir details demo-esx-opsmgr:E:\
dirId 1
dirName E:\
dirSizeLocal 81426432
dirSizeTotal 383867528
dirFileCountLocal 24
dirFileCountTotal 116
dirLargestFileSizeKB 5816158
dirOldestFileModified 17 Nov 2009
dirFileAverageAccessed 12 Aug 11:44
pathId 1556
pathName E:\