To make the form on this plugin responsive just add this to your styles.css or custom CSS.  It will add a basic level of responsiveness to the forms 

#wpcr_div_2 {
    width: 100%!important;
}

#wpcr_commentform input {
	    margin: 0!important;
	    padding: 8px!important;
	    width: 100% !important;
	    -moz-box-sizing:    border-box!important;
	    -webkit-box-sizing: border-box!important;
	    box-sizing:        border-box!important;

	}

#wpcr_commentform textarea {
    width: 100% !important;
    border-radius: 3px!important;
	        -moz-box-sizing:    border-box!important;
	        -webkit-box-sizing: border-box!important;
	        box-sizing:        border-box!important;
}

 

And in your media queries you may want to put this 

@media only screen and (max-device-width: 800px) {

#wpcr_commentform table, #wpcr_commentform td {
    display: block;
}

}