'opencv2/opencv.hpp' file not found

Header Search Path: /usr/lib** (** stands for recursive search)

It's definitely wrong. You should setup this path like:

/usr/local/include/opencv2**

or:

/usr/include/opencv2**

From your link:

In the Search Paths section set Header Search Paths to /usr/local/include (/opt/local/include if you used MacPorts)

In my case, I wrote:

/usr/local/include/opencv4

Header Search Path. I used opencv4, so I needed to add search_path a little bit deeper