You can write what you want, but if you try to publish this "vindication," your publisher will want indemnification and maybe even a surety bond. The alternative is written permission for both the use of names and approval of what you say. OK, they are not going to all do that. And if the events are reasonably well know then changing names will not disguise the names of the subjects sufficiently.
So you will be needing to buy insurance, or your publisher already has, against exactly the perils you mention.
The short of it is you should consult an attorney with experience in both defamation and privacy law (that combo is probably findable easily). Expect to pay for the advicxe, which will save you heartache and probably cash an hassle as well.
Information here is general, does not create a lawyer-client relationship, nor a substitute for consulting with an experienced attorney on the specifics of your situation.
Be very careful how vindictive you get. The truth is usually a defense when you are reporting facts, but if you stretch the truth in the name of vindication, you run the risk of liability for defamation or libel, maybe even "false light."
If what you are writing is your experience and the interaction with others is first hand and does not stray from the truth, you are probably free from liability, but not necessarily free from conflict, since it's pretty easy to find an attorney to sue anybody for anything. I agree with others who have suggested that you consult with an attorney who can vet your memoirs. I also agree that insurance may be needed to publish the book. I would also suggest, if you can, that you compile any external evidence you can locate to support the facts you will present in your memoir.
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