The FillFactor is a setting the specifies how full to build the leaf level nodes of an index. It is only applied when an index is created and is not maintained afterwards. You would specify a fill factor to account for the growth that a table will undergrow and hence, provided space for new keys, delaying node spliting.

DBCC SHOWCONTIG will return information about the fragmentation of your table or index. It will actually show external and internal fragmentation. External being the use of extents and internal referring to the use of space on a page.

Refer to the Scan Density as a measure of external fragmentation and Avg. Page density (full) for internal fragmentation.

-Mike