This is an excellent breakdown. The one thing I would quibble with is the characterization of summer salary. It's better to think of the 9-month pay idea as an accounting trick that has two purposes:
1. A benefit for faculty, since they get to be paid extra if they get grants.
2. An accounting approach for the NSF to limit how much any one faculty member can get in grant funding and account to Congress that the faculty are actually participating in the research.
It does, as the article says, create the possibility of significant swings in compensation, similar to a bonus scheme.