Close comments on articles over certain number of days is my suggestion:
Admin Dashboard>Settings>Discussion>Other comment settings>check the box at: "Automatically close comments on articles older than" and enter number of days (small number is best to stop spam on older posts)
and add the following to your comment blacklist:
other bad words
which makes any comment with such words go to comment spam.
There are also many anti-spam plugins (but they do not purport to, and in my experience, do not catch all spam comments)