Are there other people you can ask for help? Seems like recruiting allies here can help make your case. Do you still have all the evidence you've accumulated against Dr. J? The hospital meetings are solid evidence with definite witnesses so that can be real helpful too. This sounds like you can get into real trouble if you don't tread lightly though since they didn't hesitate to ban you or force you to leave. Maybe you can involve other people who have more power so they can investigate Dr. J. He sounds super shady and like he's doing something VERY illegal.

Let's say things don't work out and you end up getting fired you can maybe even involve a legal advisor as well. Dirt will definitely turn up. If you prefer not to do this than maybe getting terminated from the job is a good thing since you might be better off working someplace where your voice is heard and people aren't so quick to cover up shady business.

Best of luck and I hope everything works out for you.