You need to consult with an attorney and/or a disability advocate with experience in disability accommodations disputes. If you have difficulty promptly contacting such a professional, then you may want to meet with representatives from the United States Equal Employment Opportunity Commission (“EEOC”) or your state Fair Employment Practices agency (“FEP”). Based on what you have written, you probably should file a charge of discrimination challenging your employer’s denial of disability accommodations ASAP.
Management has evidently endeavored to set you up for termination. Moreover, your immediate boss apparently does not have a basis understanding of your disability. During your new supervisor’s tenure, things have deteriorated. (I presume you worked well with your former supervisor because he or she accommodated your disability.) In light of your specific disability, requesting written instructions and responses thereto should not be reasonably viewed as a slight to the supervisor. However, it does not seem that your supervisor or the rest of management have any intention of being reasonable with you. Instead, they seem intent on pushing you out the door.
Again, I would urge you to take the aforementioned steps to file a charge of discrimination as soon as possible.