I don't believe there's a difference in the announcements these days between ones who have sinned and are disfellowshipped and ones who disassociate. If I were you, I would send a note to several witnesses you care about and tell them exactly why you are disassociating. This is your last chance to communicate with them, and they won't have to speculate about what you might 'have done.' (Tho who am I kidding, of COURSE they will still speculate, they're witnesses! Lol) Maybe you can simply say that after reading the Bible very deeply you are a Christian that no longer believes witnesses have the truth, and since you are not allowed to disagree with witnesses and still associate with them (which you believe is a crazy, unblblical law), you must separate from them.
Best to you beautiful mind, and let us know how it goes.