What legal actions do I have concerning this.

You cannot sue your employer for defamation, slander, etc. in this context, because there is a "qualified privilege" for parties to assert their...

I need to know if I am classified as exempt correctly. I think I am working in a gray area.

To be exempt as a managerial/executive employee, you must supervise what amounts to at least 2 full-time employees. So you do not fall under the...

Should I go to the interview if I filed an EEOC charge?

You would have to have a very good reason, such as actual retaliation / harassment by the City, to have any legal excuse not to continue with the...

Do I need to return paycheck (automatic deposit) paid one month after leaving company?

Yes. And if you don't notify them / return the $ -- they will very likely find out soon (when they do an audit), then they can sue you for the...

Mr. Angel is correct. Signing the document simply shows that you read it, and had notice of it -- not that you agree with it. Best to make this...