Although I think I would have a decent case against him, I can't afford legal fees right now. And 70% of our clients were law firms who would be more than happy to represent him.

My separation notice said "Unable to perform job duties", which makes no sense, since I worked there for nearly 2 years with positive reviews and multiple successful projects.

But apparently I'm not working because I want to go home at 6pm and take my unpaid lunch.

100% of employment law firms would be more than happy to represent you. If the case is as cut-and-dried as you make it sound fees will probably not be an issue, they will work on contingency.

At least talk to a law firm and see what they think

> Call up an employment lawyer. Firing someone for not working on their vacation is wrongful termination.

In which jurisdiction?

IANAL. In the US. You can argue that there's an implicit assumption that you will not work on vacation in the employment agreement. Most of the US states are at will states, i.e. a person can be fired for no reason at all, but having a wrong reason, especially when documented in a termination letter, might be a cause for litigation.

No it's not.

And even if it was, reporting it to the DOL and let them handle it would be a thousand times less stressful and cheaper.