What is the Red and Green Percentage % That I see? What Is It Comparing To?

It's all based on the settings you have here in your Date Comparison Settings.  

The default is Prior Period, so if you have a week in the date picker (top right), it will compare to the prior week.  A month, it will compare to the prior month.  (Think of that as a mirror image of what's in your date picker.)  So if Nov-Jan in the Date Picker is about 3 months, this is comparing the data from Aug-Sep.  Just like Google Analytics). 

If you change it to "Prior Year", it's of course a Year/Year comparison for the period selected.   

You can also turn it off too! 

Can I Set Different Time Periods For Individual Widgets in the Same Dashboard?

At this time, only one Date Range per Dashboard (but of course you can have different date ranges on different dashboards).

We may consider this in the future, but we researched and learned a lot over the past few years. We noticed that the complexity of the user interface is directly related to the lack of its use. This is why our widgets are "pre-built" in the sense that users can obtain the information they're looking for without having to "search" for it and the main modifier you can do is the Date Picker in the upper right corner!