Yes, you can delete your Terms from the same page you'd use to edit them.
Note that when you delete a set of Terms, fans will no longer be able to see it and send their requests through it.
Once deleted, sets of Terms can not be restored.
If you delete or close a set of Terms, it will not affect any request you may have ongoing. The requests will still be valid with the content and price set at the time you accepted them, and will not be automatically canceled.