For the TECS instructors out there, would you say that if a student reaches a certain point in the program, that they can generally complete the rest of the program successfully? What are the biggest stumbling blocks that students encounter?
This is highly dependent on the student.
I personally do not feel there is a "certain point" in the book that is a milestone for indicating the successful completion of the remaining chapters. In particular, the first few chapters are hardware-centric, while the rest of the chapters are software-centric.
In my experience, the biggest "stumbling block" is not managing one's time correctly to allow for completion of the work; not spending enough time studying the reading (or even reading at all); and a lack of proficiency with a productive programming language, which is necessary for finishing the work during the course of one semester.