Some of the exit interview will be by based on what they want to ask. They want to be able to prove later that they were not discriminating against you. They also want to be able to judge if you will be suing them.
If you work for a big enough company there may even be a process in place regarding the form and length of the interview.
What you want to know is for these questions how open can/should you be? And when they ask you if there is anything else you want to discuss, what should you.
You must be aware of the people involved in the interview. For the "required parts" HR may be involved, or they have provided the questions. Most managers will record your answers with little comment, if you stick to the facts. Management may be glad you are going, or they may be sad you are leaving. One was embarrassed because it was viewed as a failure of his part of the organization.
Other managers will not want to hear anything you have to say after the required parts, or if you try to expand on your answers. Perks were outstanding, their management style was exemplary, working conditions were model. In other words you were like a family. Anything you say will not help. They might silently listen to you while thinking what a jerk. Others will be vocal and you will end up in a shouting match.
There is nothing to be gained about discussing these topics if management is like this. Nothing you suggest will change who they are, nothing will trickle into their culture to help you co-workers or future workers for that group.
In some cases management will accept what you have to say. They may not understand the view of the average worker. They may be concerned that the company needs to improve. They may grow because of what you say.
It doesn't come down to topics that are safe. Any topic can be discussed, or minimized based on how vocal you want to be, and how receptive management is. In your list you used the word complain. If you are there to complain, then keep that to a minimum. Just state that the conditions, deadlines, work hours were the reasons you are leaving. Management and pay are valid topics. For your situation they might not be, but for others they will be.
If you do have specific, constructive comments, and the audience is right, then discuss those topics in detail. Otherwise keep it to a minimum.