If I had known that I would have this much trouble with my feet, I wouldn't have become a teacher. I have found that principals and assistant principals are much like your boss, unsympathetic and critical. They consider you unable to do the job if you are limping or in a wheelchair. Experience has taught me that classroom control is much, much more difficult from a sitting position. Right now, I'm considering attending graduate school to become a guidance counselor so I can have contact with kids and help them, while sitting most of the time. I'm sure that you are becoming a teacher so you can help kids and make a difference in the world; however, it is a very physically demanding job. A few other ideas would include becoming a school social worker or placement coordinator.
Good luck, and I hope you find some relief from your PF soon.