The default value for the fillet, what you call starting value, is remembered between uses. So, if you make a fillet of 0.1, the next time you make a fillet, it will start at 0.1. If you make a fillet of 0.25, the next time it will start at 0.25.
The default increment is set in Tools, Options as described here:
If you change the increment in the Modify dialog that John showed, it will only change the increment for that "session" of using the dialog. The next time you bring up the Modify dialog, the increment will be back to the default increment as set in Tools, Options. If you check the Make Default check box when changing the increment in the dialog that John showed, then it changes the increment in Tools, Options so it that becomes the new default increment each time the Modify dialog is invoked.
These are all system settings, not document settings, so there is no need to save templates; the values are all stored in the Windows registry.
I hope this helps,