I can keyboard shortcut to rewind to the beginning 2 ways: control/home and W. What shortcut adjusts rewind in small increments?
Thanks

Numeric Keypad 4 (Forward is 6).
you have to be in Zoom/Scroll Mode (Num 1)
 

Alternative is to use markers and Ctrl-Shift-PgDn and -PgUp to go to Next and Previous markers respectively
 

Brandos info is right on.
you can also key bind RW or FF to some keys if you wish. just go in to preferences and keyboard shortcuts.

I have always assigned the right arrow key (use any key you like of course) to 'go to end of this measure or the next measure' and the left arrow key to 'go to  the start of this measure or the previous measure'. Single pushes then advance or rewind by measures whilst holding the key down acts as ff/rw.
 
Assignments are made under Preferences > Customisation > Keyboard shortcuts.