Elefanten att är hans vän dör! (is that proper use of "att," anyone?)

Sin is reflexive so that only can be used if you have Han/Hon/Den (respectively a name etc.) as a subject and the object is belonging to him/her/it.

For example: He is kissing his (own) wife - Han kysser sin fru He is kissing his (someone else's) wife - Han kysser hans fru

You can also have a look here: http://www.thelocal.se/blogs/theswedishteacher/2010/03/25/sin-sitt-sina/

en vän, 'a friend' is a more serious thing. en kompis is more like 'a mate', 'a pal', or 'a buddy' – it's more colloquial and refers to a less deep relationship.

I don't think so, that is why there is flickvän and pojkvän to distinguish their genders.