You need to talk with your lawyer and determine her strategy, including involving DFEH and/or EEOC, if she hasn't already involved them.
Changing your supervisor is not a reasonable accommodation required by the ADA. Your employer probably knows that and is acting accordingly.
I don't think that you should assume that an unsatisfactory rating from your current supervisor will prevent you from finding another job with your company. You can point to your recent bonus, your prior good ratings and satisfactory relationships with other supervisors. You can honestly say that your supervisor's management style is toxic to your health and everybody realizes that a new supervisor/job change may be the best solution. Will any of the supervisors/managers with whom you worked previously consider giving you a job?

