I also have cptsd.
Can't help much with the legal questions. But there's medication that can reduce nightmares. Prazosin in particular. It blocks the adrenal response, so you are less likely to go into fight or flight while sleeping.
Also, PTSD is recognized as a disability. It's not easy to get disability for it, however discriminating against you for having it, when you are requesting reasonable accommodations is absolutely illegal. If you have medical documentation of your condition that will be helpful. If you don't, I suggest you start figuring out how to document it. I see a trauma therapist, and my GP is also aware that I have it, as he's the one that gave me the medication. This is the documentation I'm currently using to try to get disability and it would also work in your instance.
You can grab a copy of entrepreneurial small business 5th edition used for probably 20 bucks. I'm about one semester out from a business administration associate's degree. That textbook was the most comprehensive of anything that I studied over the last year and a half. And the only textbook I made sure to buy a print copy of, so I have it for reference.