Hi Jay,
For the percentages you can create a formula like this:
distinctcount({database_field}, {Group Field}) / Sum({database_field}, {Group Field})
Replace {Group Field} with the Name of the field used to group the report. I guess in this case this would be the Incidents group?
Similarly the {Group Field} in the denominator part of the formula would be a higher level group.
-Abhilash
