Yes. What I said here is exactly what I would do if the situation ever occurred.

We're not talking the next Harry Potter here, we're talking maybe $50-100 for an article, usually less. What you're discussing is more appropriate for a major movie or similar.

And at risk of been accused of being 'patronising', ideas cannot be copyrighted. An editor getting your idea means nothing. An editor getting your written work (which you have proof that you sent them) and publishing that is a copyright violation. If said editor does that, you contact the publication's legal team and lodge a complaint of copyright violation. Send them a DMCA takedown request too.

Sure, the editor can claim the emails are forged, I can claim the sky is pink, you can claim that the editor promised to pay you a million dollars, doesn't make it true. Claims without prove are just hot air and the burden of proof is on the one making the claim. Proving that said emails (which you would have sent to the publication's company email server, resulting in a log trail, and have all your own records of) are fake is a whole nother matter and hard.

An editor that does this won't have a job for long. A publication that does this won't be in business long.

Copyright these days favours the author, probably too much to be honest.