If moving to anesthetics doesn't work out, I'd suggest investigating HIM (if you are interested in staying in health care, that is). I suffered severe injury to my spinal cord almost a decade ago and am currently pursuing a bachelor's degree in HIM (I'm specifically tailoring my degree towards health informatics). It might be worth investigating for you, as it's a field that is growing rapidly and can accommodate those with physical disabilities. The AHIMA (American Health Information Management Association) website might be of some use to you: www.ahima.org
I'm not sure if there's an international or Australian version.
Your situation sounds awful, and I wish there were something I could do to help. I've been in that spot (albeit in another field); you're under pressure to stick it out against short staffing, you're in terrible pain, and you're looked down upon when you finally have to push for restrictions to your duties for the sake of your ability to keep working at all. It's miserable. A little piece of your soul drains to newsprint grey each day you have to work under those circumstances.
It helped me to know I was working towards a new, better opportunity. Perhaps the law studies you mentioned could provide that kind of hope or goal for you; if not, HIM could be a good option, or you could pursue more advanced nursing education (nursing informatics, for instance). I don't know what your country has to offer disabled workers, but the US has an agency that assists people to pursue educational and employment opportunities better suited to their talents. It also provides help with assistive devices, like improved workstations or appropriate seating. Perhaps you could investigate whether your country offers anything similar.
I am thankful that your DON has been supportive. Don't worry about being one of "those nurses" who require work restrictions. Your behavior has been beyond exemplary, but you are doing nothing wrong by requesting accommodation! Your employer will not
look out for your health. It is uncomfortable to have to advocate for yourself in the workplace, but it is necessary under the circumstances. I know how awful it feels to roll around restlessly in the night, dreading the start of the next workday. The best suggestion I can offer to combat the depression and anger is to pour all that frustration into pursuing new employment and educational opportunities. Having a clear-cut goal in mind and working towards it can really help enormously. Sometimes it helps to vent to someone completely outside the situation, so please feel free to PM me if you need a listener without a connection to you or the situation. Journaling, as an earlier poster suggested, can also be very helpful.
I hope you find a terrific new path perfectly suited to your strengths and talents. I wish you the best of luck - you certainly deserve it!