The layout name is not part of the meta key, I’m not sure about your code but it might be
$column_module = get_post_meta( $post_id, 'section_layout_'.$count.'_single_col_elements_content_type', true );
A nested flex field, or fields would be something like
"{$flex_field_name}_{$index}_{$nested_flex_name}_{$index}_{$sub_field_name}"
