How to make all label fields full width

You first need to go the SCRIPT section and add isLabel() function:

function isLabel(field) {
  return CONTAINS(DATANAMES('Label'), field);
}

Then, you will need to use this function in the BODY section just before the last <% } else { %>:

<% } else if (isLabel(element.dataName)) { %>
      <div class='field'>
        <b><%= element.label %></b>
      </div>