Is it possible to get the rospy lib into PyCharm for autocompleting and highlighting error without installing ROS on my MAC?
PyCharm Professional edition allows for the use of Remote Interpreters. You would need to install ROS either on a remote machine or a local VM and then connect PyCharm to it over SSH. You can also use a Docker Interpreter and simply install ROS in a docker container. For simplicity you could start with an existing ROS Docker container.
Either way, you'll need to ensure that the environment is effectively activated so that PyCharm can find the ROS python packages and not just the OS packages.