Paul, I made some changes to your account. I don't know if it had any effect but try it. If not, just so I understand what you're trying to accomplish bear with me, This is one of several parts of the software that is very confusing in the back end, and possibly buggy I don't know yet.
You want to stop receiving emails about this thread (or any thread you choose), correct? You have clicked the unwatch button, "but it doesn't DO anything". After you clicked it, have you still been receiving notifications?