There is a saying that "It is good to be the King." The business cannot afford to give everyone 6 weeks of vacation, but it can afford to give the Boss 6 weeks. Only a doctor can make you better, and he was the one who prolonged your treatment. They can try PT/Epidurals/MRI within 60 days and surgery within 90 if warranted. That is how back surgery happens if it is non-work related. Sorry you lost your job.
We give free general concepts to be helpful, but you should give ALL your facts to a licensed Attorney in your state before you RELY upon any legal advice.
Talk to a WC attorney and he will review your case. If you were terminated due to the work related injury you may have a wrongful termination case. But I would suggest you talk to a WC attorney to review your case and based on such make a more educated determination. Good Luck!