try this :
<?php
$options = [
'fa-address-book' => ' ',
'fa-address-book-o' => '',
'fa-address-card' => ' ',
'fa-address-card-o' => '',
'fa-adjust' => ''
// etc.
// I have full list of this array let me know if you are interested in.
];
return new \IPS\Helpers\Form\Radio("core_theme_setting_title_{$row['sc_id']}", $value, FALSE, array(
'options' => $options,
'class' => 'radio-class-faicons',
'parse' => "raw"
), NULL, NULL, NULL, 'theme_setting_' . $row['sc_key']);
add this class to your custom css file :
.radio-class-faicons {
font-family:'FontAwesome' !important;
font-weight:900;
}