Employment Law Questions? Ask an Employment Lawyer.
How many employees does the employer have?
Do you have an employment contract stating that the terms of your employment cannot be altered without your consent?
Ok. The issue here is that your time off due to the medical issue what not protected time off. For you to have protected medical leave, you have to have an employer with at least 50 employees. So, they right to return to your same job duties, pay, and benefits don't really exist here.
Without an employment contract then, they can alter your benefits at any time, with or without cause. Regrettably, that means that they could reduce your hourly rate and insurance benefits. They can also reduce your leave and sick leave benefits for the future...but that doesn't apply to currently accrued time off.
Now, the taking of your leave and sick time only makes sense if they paid you for the time you were off. Otherwise, they can't deduct you from you paid time off without paying you for that time. For that, you could technically sue them in state court for breach of contract. Unfortunately, your state doesn't do their own "wage claim" process, as do many other states (through a Department of Labor), so you are left to fend for yourself in state court/small claims.