Hello,
1) You can use product category description http://prntscr.com/hda1s4 (Make sure that CMB2 plugin is enabled)
2) Where have you done your changes? In theme or core plugin files? Then you will lose them after the update. All the changes should be placed in child theme. Also, when we discussed this question time ago I told you that this sorting option is WC plugin option, it’s not our theme option, so by default, our theme does not include code related to this sorting (including translation). If you want to translate these texts you can do this using WooCommerce translation files.
Regards