My advice, save some money, get your resume ready and sue. If they fire you, then sue for retaliation as well.

Suing your employer is often viewed in an extremely bad light by future employers. I'd even go so far as to call it "career suicide."

You'd have to be at a pretty high level for a future employer to do a public records search on you (not to be confused with a background check), thus the compensation you would receive for a retaliatory firing would likely be in the millions (or tens of millions) of dollars as it is often based on lost income and has a punitive component. You'd likely never have to work again.

Many employers of mine have done background checks on me prior to extending an offer. And there's this hip things the kiddos are using called "Duck Duck Go".

Well this individual did those first two things. I think damage has been done to the company already even if litigation wasn't involved. Sadly a lot of companies only get the message when they need pay damages. I get the impression that money doesn't seem to much of a concern for this company however.

You missed a step, which is "make sure you have a competing offer in hand".