If you do meet with the elders, and the JC about a 'sin' that occurred many years ago, why not dig out a few scriptures about Jesus alone being able to atone and forgive sins, point out that you've gone to him and asked for forgiveness, you know that you have been forgiven and that you feel great.
Crucial to legal actions taken against the Watchtower Society has been the “Three Year” rule. This allowed for known sex offenders to continue serving as elders, provided any known offenses were committed at least three years prior to confession. The Watch Tower Society's 1972 book,Organization for Kingdom-Preaching and Disciple-Making stated: "If a person was serving as an elder or a ministerial servant when he committed a serious wrong, even though it was some years ago, he bears a degree of reprehensibility, for he continued to serve in that position though knowing that he had, for the time at least, disqualified himself, not being then “free from accusation.” (1 Tim. 3:2, 10; Titus 1:6,7) He should have informed the judicial committee that he did not adhere to the requirements and should have stepped down from his position. In view of his failure to do this at that time, he would now be removed from that position."
The term “some years ago” was clarified shortly afterwards in Our Kingdom Ministry October 1972, p.8, as a time period of three years:
What was meant by “some years ago” on page 170, paragraph two, in the “Organization” book? This indicates more than a year or two. It may be noted that it did not say “many years ago.” So it is not the exact number of years, but more like two or three years. It was not intended to have a brother go back into the distant past to bring up wrongs of which he repented years ago and that have evidently been forgiven by Jehovah and are not practiced now
If you want to take a quick read at our non-DA letter that got us DF'd :-) then its here
Time over again I wouldn't attend a JC or write a letter - I'd just let them know I'd made an informed decision not to attend meetings for the time being and I'd be sure to let them know if I need anything. After that, what will be will be.
You haven't ceded control to their procedures and you haven't incriminated yourself - the rest belongs to karma :-)
Enjoy the rest of your life - its starts today.