Medawar has come across several Americans who have become embroiled in, and threatened by, American organized crime gangs and stalking gangs, who all tend to say that they cannot go to the police, or even the FBI, because the gang includes members of their local FBI field office, or that the gang is run by ex-CIA men with "connections."
This link explains the official procedure for dealing with this.
It's worth a read. But you have to make up your own mind if it will work for you, in your circumstances.
However, if you know anything at all, even if it's a snippet which seems useless on its own, about the movement of drugs and other contraband, or the proceeds of crime, in and out of the United States, or between two other countries, that involves the people who are threatening or harming you, (or their associates) then you can try this link here. This is worth a try, because:
It's hosted in the UK, and is secure. None of the people running it are impressed or frightened by rogue redneck FBI agents and their buddies.
The people running it have very powerful computers and lots of other snippets of information, so even a tiny piece (which no-one could trace back to you anyway) might fit someone else's info and make a breakthrough.
Nearly all of America's organised crime gangs run contraband through the waters of UK-protected countries, allowing the Royal Navy to intervene. Regardless of whether the FBI and DEA really want them to or not! Those who don't run actual goods through British-patrolled waters, tend to run money through banks in British-controlled jurisdictions, such as the Virgin Islands or Gibraltar. British customs authorities can get cooperation out of countries, such as Cuba, that would never cooperate with the "Feds" in a million years.
It gives you, if your information is genuine, a chance to torpedo (perhaps literally) the gang making your life hell. And these gangs have a lot of internal tension, because everybody is breaking the law and depends for their life on liberty on other corrupt people they don't really trust in the dark anyway.
Once the gang's activities get exposed, perhaps by a maritime stop and search that bent FBI agents are powerless to prevent, your tip-offs about it through the "proper channels" in the first link will be pushing at an open door, rather than a brick wall!
One of the reasons why the druggies had it their own way in Columbia for so many years, was that American authorities had a monopoly on the intelligence war there. British agencies such as SOCA, HMRC and even MI6, are running agents in Columbia now, and because these agencies aren't actually run by ex-CIA men using drugs deals as a pension fund, they are having an effect.
Anything you post on the HMRC secure hotline page will get to these agencies in due course.
There is a page of instructions, worth reading, although some of it's about tax, VAT and duty, which probably doesn't affect you, and then there's a secure form for giving information.
Give it a whirl. It isn't guaranteed to save your life, but it might give the criminals something to worry about other than you, and it might just unravel the gang in time to help you, after all. And if not, there's still a chance that you might be avenged.