showEndpointHints => 0, showEndTypeHints => 0
to your cmp() calls.
In order to edit the messages you would need to install a post filter to the answer checker. (There is also another way to do it that uses a mechanism intended for allowing the error messages to be translated into another language. That could be used to convert the message to another form or to a blank message, but the *Hints flags above are probably your best choice.)
Davide