It's perhaps worth being aware that when Feynman initially gave his course at Caltech, most of the students either did extremely well or completely bombed the exam. The middle ground kinda disappeared. So if you read the Feynman lectures and struggle to understand his perspective from the first few chapters, it may be best to give up sooner than later (and move onto other sources).

Fantastic material! That being said I'd recommend to have several alternative textbooks for every subject at hand. Whenever stuck - one should switch to another and try a different take.