You have two issues here. First, the workers' compensation claim. If the doctor plans to place you at MMI, you can explain that you continue to have pain with no improvement. If this is a clinic or primary care physician, you can request to see a specialist due to your lack of improvement. If the doctor still places you at MMI, you have the right to one change in doctor per case. However, if the insurance company authorizes a new doctor within 5 days of your written request, they get to choose the new doctor. You should probably consult a workers' compensation attorney in your area to discuss this before making any decisions. You should also discuss the discrimination aspect with this attorney as they may be able to help, or refer you to another attorney. To answer your last question, no, the doctor's office should not make you sign anything with regard to being placed at MMI.
No, you should not be required to sign anything regarding an assignment of MMI, and you should refuse, if asked. If you don't agree that you are at MMI, even if the doctor says you are, you might still have the option of using a "one-time change" to another doctor in that same specialty. Before you decide to use that option, though, make sure you talk to an experienced W/C attorney, because there are long-term strategy implications in when to use the one-time change. You should also talk to the W/C attorney you see about the discrimination/harassment, because that could give rise to a separate lawsuit (against the employer, not the employer's W/C insurance company).
It is possible that you could find one attorney to handle all potential claims. However, you are discussing separate and substantially different claims - the workers compensation claim and the discrimination/harassment claim. As to your workers compensation inquiry - you should be required to sign any documents with doctor regarding your "agreement" to MMI. You should contact a workers compensation attorney to discuss your options if you feel you need additional medical care. As stated in the earlier response, you do have options to pursue alternative and additional medical care under Florida Law.
The larger questiono is why you haven't hired a lawyer yet. Trusting the workers compensation insurance company and their hand-picked doctors and nurse case managers AS well as your employer is like letting the fox watch the henhouse. Doing without a good aggressive WC lawyer may leave you without much of a case and without a job. From the moment you suffered a job injury, everyone involved in the system is planning how to minimize your injuries, return you to work even in light duty but with the plan to get rid of you after several weeks or months after returning to work. My advice is not to get in the tiny details but to see the bigger picture. There are several good WC lawyers in Tallahassee. Find one you can communicate with and trust and who only represents injured workers. Most can advise you whether you have any other type of case such as wrongful discharge or discrimination, but the first thing is to hire a lawyer ASAP.