some profile fields (sex) don't show up in field mapping

The reason it's not showing up is because we only show fields that are of free-form fields (textbox, textarea, etc) from JomSocial. If it's a drop-down in JomSocial, there's no guarantee that the response from Facebook will line-up with the available options you have configured in JomSocial (boy/girl, male/female, man/woman, or multi-lingual). Because of that, there isn't really a way to import the data from Facebook without converting it to your pre-defined options. We are hoping to come up with a way for some specific select boxes, like gender, to work with the importing, but right now, it's just not possible.

The only option I can recommend now is to change (or add a new) "Sex" field into a text field and import the data from Facebook into that field.
Hope that explains, even if it's not the answer you were looking for.

Thanks,
Alex