Try adding this to the end of template.css to hide the pseudo elements. (I think this should cover most question types)
#limesurvey input[type="radio"],
#limesurvey input[type="checkbox"] {
position: relative;
opacity: 1;
}
#limesurvey .radio label::before,
#limesurvey .radio label::after,
#limesurvey .checkbox label::before,
#limesurvey .checkbox label::after {
display: none;
}