So it sounds like you'll be going into accounting as a first-year associate.
It's going to be nearly impossible justifying those hours to your employer. As many have said, we are in client services and oftentimes, working only 8 hours a day is not enough. Leaving at 1:30pm sounds pretty unreasonable especially given the fact you confirm you will not be available after you leave the office.
Think about this scenario: You are given an assignment which you complete and then leave the office at 1:30pm. Your senior or manager reviews the work and they need you to make changes. Uh oh, wait a second, you've already left the office and you're not available. Waiting until tomorrow to do the work may not always be feasible. So what will happen? Another associate or your senior/manager will have to make the changes which takes time away from what they are doing. This scenario does not exclude client requests. Clients will make requests at all hours of the day (within reason, of course) and you have to be agile enough to meet those requests.
Leaving the office at 1:30pm is not realistic, I don't care which accounting firm you are working at whether it's the Big Four or a boutique. If the above happened and you were on my team, I would request a replacement after the first incident to nip it in the bud. If it happens enough, you won't last long wherever you are.
Also, in my experience (I work at a Big Four), having passed the CPA does not make you more desirable or give you any leverage.
FAR - 75 | REG - 87 | AUD - 82 | LAW - 81