How to Set my Mac's $PATH back the way it was before
By default the paths are saved in the file /etc/paths. You can edit it e.g. with sudo vim /etc/paths. Each line should contain one directory used for $PATH.

Then there is the directory /etc/paths.d/ that can contain text files with paths in it.

Furthermore the path can be modified in the files ~/.bashrc and ~/.bash_profile.



However, the $PATH you are stating is the default one and usually desired. Restricting it to only /usr/local/bin would make a lot of default applications - like vim, ls, or even sudo that reside in /usr/bin/ or /bin/ - inaccessible without typing their whole paths every time.