I probably completely overlooked it, but your syntax appears to be wrong.
You use
echo get_field('custom_category_description', 'option');
but you need to use
echo get_field('custom_category_description', {taxonomy}_{term_id});
So now I’m wondering why you get an output if this is the actual code, because your code retrieves an option field value and NOT a taxonomy description (or I’m not understanding your setup fully).
