What to do if my former employer is defaming about me stealing from his company?

I am in Florida and my former employer tell to Florida unemployment that he didnt fired me that I resigned when he talked to me that I was misusing company funds at my favor, he claimed that I was adding unearned bonus to my paystub, I was the office manager in a office and I was the person preparing the payroll, but every time before the payroll was submiting I was sending it to the employer for review and approval. The bonus that I and other employees get were part of our payments, on le of my bonus was base on number of products sold but he is claiming the numbers never were meet, but as I said before he always reviewed and approved bonus and payroll. My unemployment benefits were denied because this and my former employer not only fired me without valid reason he is also affecting my income benefits and my career with defamation, he didnt pay me my last day of work, he didnt pay my vacations and severance payment, the proof that he fired me and I didnt resigned my job is that he send me a written termination letter where he is also requesting money for "unearned bonus" what do I do