There is always the possibility that your ex knows you will eventually read this messages. In that case it is just a part in taking revenge. I would not use it or mention it as long as you are DF'd. it will turn against you.
Unless you start slacking, eventually you will be reinstated. No matter in this or another Congo. For adultery, minimum one year, probably 1.5 or 2. If you were at all meetings during 2 years, and reinstated, you can take other actions. Writing the CO,... I would NEVER bring up these messages as long as you are DF'd. It will only be used against you. However after reinstatement, it could be useful to let the MS know you have some skeleton in a closet that can come out anytime, unless they leave you alone,... or something along those lines