You cannot delete your account.
Ask Mark to do it manually for you. See: http://www.findagrave.com/cgi-bin/fg.cgi?page=mr&MRid=46832165
Please note that AccountKiller.com is not associated with the business listed on this page. AccountKiller provides easy-to-understand instructions and guides on how to cancel charges and relationships from the list of businesses on our site, we have no affiliation with these businesses.