(1). When you post or share a post on Facebook, make them "friends only" by clicking on the down arrow left to the Post button
(2). Use the above friends only option when you upload a photo, a photo album or a video
You can change that privacy after you upload photos/videos too.
Cover pictures are always public. You can not change it.
Profile pictures allow to edit privacy for pictures one by one.
Other picture albums allow to apply privacy for all the photos in album at once.
(4). Go to About tab of your profile
Click on Edit button of the Work and Education section
Change the privacy by clicking on the down arrows in front of each school you attend
Note: I have no idea about your issue number 3