He's about halfway through the DC's, try to go as deep as you can, and head for deeper waters, and get down as far as you can, as quitly as possible. If you use the depth mod, and can get down around 200m, you can lose the DD that's tormenting you. Put some distance between you and him, and then meter out your revenge if you wish.
I don't worry about the latter myself, just losing them is enough for me, and even if you fire an acoustic torp at them, they can still out mauever it, and come at you again as the crew are already alert to your presence.