It is surely entirely possible to get stuck in the no-man's land where you know something is seriously wrong but you cannot prove it to the level of qualifying

It is surely entirely possible to get stuck in the no-man's land where you know something is seriously wrong but you cannot prove it to the level of qualifying for the kind of whistleblower protections you need to survive the process. In this situation, blowing the whistle and failing to be heard is one outcome. Blowing the whistle and having the consensus in a light-touch regulatory system be that you're doing so without cause or worse maliciously is another. Blowing the whistle, being unable to prove it and being sued into oblivion is yet another. If you are sued into oblivion by a crook, you tend not to get your money back when they are finally caught. My own feeling is that in such a situation I would walk away, refuse to give interviews, pointedly not take a job for a while, talk to a lawyer in a way that is recorded, and likely brief an appropriate journalist off the record. Time will tell if he did.