1. The way to prove a case is (1) if A then B; (2) C is A; (3) if C then B.
(1) if I am a non-exempt employee, I am entitled to $5000 backpay.
(2) I am a non-exempt employee because ....
(3) therefore, I am entitled to $5000 backpay.
Please prove (2), starting with the definition of "non-exempt" employee.
2. Here is how I (your company) prove that you are an exempt employee:
https://www.illinois.gov/idol/laws-rules/fls/pages/overtime-exemption.aspx
You are a professional as defined in above link:
"Whose primary duty consists of the performance of work requiring knowledge of an advanced type in a field of science or learning customarily acquired by a prolonged course of specialized intellectual instruction and study; and Consistently exercises discretion and judgment"
Only those workers need close supervision such as manual labor (janitors, machine operators, bus drivers) are not exempt employees.
Every HR professional know this, your argument is easy to rebut.
3. Your old supervisor left the company might have nothing to do with your case, it is 10 years after the fact anyway. Don't get your hopes up.
Lastly, this is not a court hearing, but an administrative hearing. The rule of evidence is looser than court hearing, but the administrative judge can stop you if you ramble on like pile up irrelevant evidence like those in your post. Focus your limited time to prove you are non-exempt employee.
Good luck.