They are looking for reasons to disqualify you, not to hire you, so your main job is to avoid giving them any. The questions will be mostly behavioral, focusing on things like "tell me about a time you made a mistake", "how do you handle conflict with a coworker", and "why do you want to fly for PSA". They care far more about your personality, attitude, and decision-making process than your current technical knowledge. They want to know if you are teachable, if you can take criticism, and if you will be a safe, reliable pilot who can eventually become a captain. Your every answer should show them you are a low-risk, high-potential investment.

Bring up your entire life experience, not just your time in an airplane, because they want to see a well-rounded person with maturity. Showcasing how you handled challenges in a previous, non-aviation job can be more powerful than just talking about a crosswind landing. They know they will teach you how to fly their jets, but they can't teach you to have a good attitude or a solid work ethic. You have to prove you already have that. Regarding your other question, you will get full flight benefits once you are officially an employee in the program. My team actually built a tool over at interviews.chat that's been helping candidates walk into these kinds of discussions and clearly show they're the right person for the job.