You should totally watch the end of LoK, it's really good. I don't want to spoil anything, but it handles a certain pairing incredibly well.

Air and fire work fine for me. I think I'll make air male and fire female.

Yes please, I'd love to be able to get started on my characters. 

I like the idea of the evil force spreading some sort of disease. Maybe something that, when it infects benders, it somehow corrupts their bending? Or stops them from being able to use it?