I've cured vilkas and farkas. But when I try to open up the quest for Aela she only gives me Animal Extermination quests. Also, Can I cure myself by just going to the flame and using a witch head on my own?

What the?....???

aela doesnt want to be cured, so she never gives you the option.
you can cure yourself just like you described.

oh.. Cool thanks.

is that lavey in your avatar?