On your first comment what I was suggesting was using formula to create; -

1. a positive / negative text value to act as a group for the logic of whether it is positive or negative graphs

2. an absolute value for your values

Using the combination of the two 100% will be 100%, just 100% of positive and 100% of negative, as I alluded to if you do not do this then your divisor could wind up with ridiculous results as the balance between positive and negative brings it closer as a whole to zero.

On your second point you might want to looking into using jscript, but if like me you prefer to keep it vanilla then radar graphs are a good near alternative.