It's pretty important to note this is about how to teach C, not why. Should schools be teaching C at all? I would say yes, not as an introductory language but as a precursor to studying kernels or databases or compilers. Real-life examples of these are mostly written in C, and studying such systems is IMO a necessary part of a CS curriculum. Therefore, at some point students need to learn C. They should certainly have the option, so we still need to address the question of how it should be taught.

With regard to that question, the OP seems pretty spot one. The identification of certain codebases as good or bad matches my own experience with most of them. The advice to use static analysis and to avoid preprocessor abuse is sound. There are only a few things I'd add.

* You can't really learn C without also learning to use a debugger - probably gdb. That must be part of the lesson plan.

* A more in-depth discussion of good error-handling and memory-management practices would be worthwhile, since C itself doesn't provide these.

* It can be very informative to implement some of the features found in other languages in C. Examples might include a simple form of object orientation, or a map/dict/hash, or a regex parser. Besides their value as a form of practice, this would expose students to some of the issues and decisions involved in making these a built-in part of a higher level language.