Your access to the forum will be removed in the month following your membership lapse. Of course, you could change your password on the last day of your membership. Your user account probably cannot be completely removed from the system because it could involve deleting entire threads, but your email address could probably be changed to something invalid. You would need to contact Jeff Betz at the club's office to make something like that happen, the forum moderation team can't do that.
Why would you want to remove all your posts on the forum??? A forum turns into a knowledge base and removing posts from it would be removing some of that knowledge.