As opposed to legal theory, I don't think you can assure that they have purged all your records. They have lawyers who only represent their interests. Compared to a single individual, they already have detailed legal memos and probably canned briefs ready to go. The religious status makes it very hard to fight them. No court will impose itself in internal disputes. They can assert a religious privilege.
Theocratic warfare principles are a major barrier. I can envision them relishing keeping tabs on you. If it is a specific situation that may involve libel, slander, or some concrete detriment to you if shared widely, a legal letter might make them back down. No outside lawyer will be allowed access to your records. You are not only fighting the WTBTS, which obviously has no regard for privacy, but your local elders' discretion. Asking for info might make them retain it even more.
If the record is routine, what does it matter? Your fears grant them legitimacy. If it is not a routine situation, a local lawyer might help. The fee for a simple lawyer should be relatively small since the lawyer is not doing much.
Privacy is more and more important in American society. I believe the language in Roe v. Wade concerning the penumbra of the const'n was correct. Roe is cited in many nonabortion settings. American courts are trained to protect religious freedom for religions. I believe if people like us agitate a gradual change can emerge. Courts note the difference in Europe frequently.