Grip strengths are categorized as strong, standard and weak; select one that is best for you and learn to groove your swing with it
Changing your grip is uncomfortable so the best place to work on it is at home, holding the club a few minutes at a time until it feels comfortable enough to swing with
When an instructor refers to open and closed first you must determine if it is the body or the clubface he is talking about, an open clubface has the face aimed to the right while an open stance has your body aimed to the left