I really wish for you that you could go part time! Inflexible institutional thinking always bugs me. From an outside view point, it sounds like the demand is never ending, so the weekly cap is somewhat arbitrary. Its not set to meet every patient's needs for that week, or your needs as a surgeon and human being. It's just the maximum number of people (plus two layers of back ups) the administrators think can be squeezed in. Sure, they wouldn't be able to meet everyone's needs if they lowered your hours- but they aren't doing that now, either!
Not being able to go back is a tough one. How long do you think you could go without working and still return to your field? Would it be possible to test the water with a long vacation?
I have two friends who 'retired' early from successful engineering careers in their 40's. They had their kids later in life and both seem okay with their choice to stop working. I can tell that the loss of identity has been hard for both of them. One left her job seven years ago and one around five years ago. I've noticed that both of them still, to this day, when meeting another mom (including other SAHMs) will immediately bring up that their former job titles and companies, and feel like they need to explain why they became SAHMs. We're all busy moms so it's not like we don't get it! But, that said, I've never heard them express any regret over leaving.
Another friend of mine took a sabbatical from a very stressful job in mental health to test the waters on being a SAHM. She thought she would love it. She did not. Within two months, she'd joined one of those co-op style office suites and spent the sabbatical writing a book in her field. She's changed fields a bit as she realized she liked working, but she didn't like being in such a stressful position. In that way the sabbatical was really good for her. Is there any way you could do something similar and see how you like it? It might be that stepping away would give you a new perspective.