$arr['Zumpito_event_full_day'] = isset( $_POST['Zumpito_event_full_day'] ) ? esc_attr( $_POST['Zumpito_event_full_day]) : '';
this should solve your first notice
explanation is this in the link given by you
$arr['Zumpito_event_full_day'] = isset( $_POST['Zumpito_event_full_day'] ) ? esc_attr( $_POST['Zumpito_event_full_day]) : '';
this should solve your first notice
explanation is this in the link given by you